The Firebird 5.0 Language Reference | Context Functions

`RDB$GET_CONTEXT()`

Retrieves the value of a context variable from a namespace

Result type

VARCHAR(255)

Syntax

RDB$GET_CONTEXT ('<namespace>', <varname>)

<namespace> ::= SYSTEM | USER_SESSION | USER_TRANSACTION | DDL_TRIGGER
<varname>   ::= A case-sensitive quoted string of max. 80 characters

Table 1. `RDB$GET_CONTEXT` Function Parameters
Parameter	Description
namespace	Namespace
varname	Variable name;case-sensitive with a maximum length of 80 characters

The namespaces

The USER_SESSION and USER_TRANSACTION namespaces are initially empty.A user can create and set variables with RDB$SET_CONTEXT() and retrieve them with RDB$GET_CONTEXT().The SYSTEM namespace is read-only.The DDL_TRIGGER namespace is only valid in DDL triggers, and is read-only.The SYSTEM and DDL_TRIGGER namespaces contain a number of predefined variables, shown below.

Return values and error behaviour

If the polled variable exists in the given namespace, its value will be returned as a string of max. 255 characters.If the namespace doesn’t exist or if you try to access a non-existing variable in the SYSTEM or DDL_TRIGGER namespace, an error is raised.If you request a non-existing variable in one of the user namespaces, NULL is returned.Both namespace and variable names must be given as single-quoted, case-sensitive, non-NULL strings.

The `SYSTEM` Namespace

Context variables in the SYSTEM namespace

CLIENT_ADDRESS: For TCP, this is the IP address.For XNET, the local process ID.For all other protocols this variable is NULL.
CLIENT_HOST: The wire protocol host name of remote client.Value is returned for all supported protocols.
CLIENT_PID: Process ID of remote client application.
CLIENT_PROCESS: Process name of remote client application.
CURRENT_ROLE: Same as global [fblangref50-contextvars-current-role] variable.
CURRENT_USER: Same as global [fblangref50-contextvars-current-user] variable.
DB_FILE_ID: Unique filesystem-level ID of the current database.
DB_GUID: GUID of the current database.
DB_NAME: Canonical name of current database;either the full path to the database or — if connecting via the path is disallowed — its alias.
DECFLOAT_ROUND: Rounding mode of the current connection used in operations with DECFLOAT values.See also SET DECFLOAT.
DECFLOAT_TRAPS: Exceptional conditions for the current connection in operations with DECFLOAT values that cause a trap.See also SET DECFLOAT.
EFFECTIVE_USER: Effective user at the point RDB$GET_CONTEXT is called;indicates privileges of which user is currently used to execute a function, procedure, trigger.
ENGINE_VERSION: The Firebird engine (server) version.
EXT_CONN_POOL_ACTIVE_COUNT: Count of active connections associated with the external connection pool.
EXT_CONN_POOL_IDLE_COUNT: Count of currently inactive connections available in the connection pool.
EXT_CONN_POOL_LIFETIME: External connection pool idle connection lifetime, in seconds.
EXT_CONN_POOL_SIZE: External connection pool size.
GLOBAL_CN: Most current value of global Commit Number counter.
ISOLATION_LEVEL: The isolation level of the current transaction: 'READ COMMITTED', 'SNAPSHOT' or 'CONSISTENCY'.
LOCK_TIMEOUT: Lock timeout of the current transaction.
NETWORK_PROTOCOL: The protocol used for the connection: 'TCPv4', 'TCPv6', 'XNET' or NULL.
PARALLEL_WORKERS: The maximum number of parallel workers of the connection.
READ_ONLY: Returns 'TRUE' if current transaction is read-only and 'FALSE' otherwise.
REPLICA_MODE: Replica mode of the database: 'READ-ONLY', 'READ-WRITE' and NULL.
REPLICATION_SEQUENCE: Current replication sequence (number of the latest segment written to the replication journal).
SESSION_ID: Same as global [fblangref50-contextvars-current-connection] variable.
SESSION_IDLE_TIMEOUT: Connection-level idle timeout, or 0 if no timeout was set.When 0 is reported the database ConnectionIdleTimeout from databases.conf or firebird.conf applies.
SESSION_TIMEZONE: Current session time zone.
SNAPSHOT_NUMBER: Current snapshot number for the transaction executing this statement.For SNAPSHOT and SNAPSHOT TABLE STABILITY, this number is stable for the duration of the transaction;for READ COMMITTED this number will change (increment) as concurrent transactions are committed.
STATEMENT_TIMEOUT: Connection-level statement timeout, or 0 if no timeout was set.When 0 is reported the database StatementTimeout from databases.conf or firebird.conf applies.
TRANSACTION_ID: Same as global [fblangref50-contextvars-current-transaction] variable.
WIRE_COMPRESSED: Compression status of the current connection.If the connection is compressed, returns TRUE;if it is not compressed, returns FALSE.Returns NULL if the connection is embedded.
WIRE_CRYPT_PLUGIN: If connection is encrypted - returns name of current plugin, otherwise NULL.
WIRE_ENCRYPTED: Encryption status of the current connection.If the connection is encrypted, returns TRUE;if it is not encrypted, returns FALSE.Returns NULL if the connection is embedded.

The `DDL_TRIGGER` Namespace

The DDL_TRIGGER namespace is valid only when a DDL trigger is running.Its use is also valid in stored procedures and functions when called by DDL triggers.

The DDL_TRIGGER context works like a stack.Before a DDL trigger is fired, the values relative to the executed command are pushed onto this stack.After the trigger finishes, the values are popped.So in the case of cascade DDL statements, when a user DDL command fires a DDL trigger and this trigger executes another DDL command with EXECUTE STATEMENT, the values of the DDL_TRIGGER namespace are the ones relative to the command that fired the last DDL trigger on the call stack.

Context variables in the DDL_TRIGGER namespace

EVENT_TYPE: event type (CREATE, ALTER, DROP)
OBJECT_TYPE: object type (TABLE, VIEW, etc)
DDL_EVENT: event name (<ddl event item>), where <ddl event item> is EVENT_TYPE || ' ' || OBJECT_TYPE
OBJECT_NAME: metadata object name
OLD_OBJECT_NAME: for tracking the renaming of a domain (see note)
NEW_OBJECT_NAME: for tracking the renaming of a domain (see note)
SQL_TEXT: sql statement text

Note	`ALTER DOMAIN old-name TO new-name` sets `OLD_OBJECT_NAME` and `NEW_OBJECT_NAME` in both `BEFORE` and `AFTER` triggers.For this command, `OBJECT_NAME` will have the old object name in `BEFORE` triggers, and the new object name in `AFTER` triggers.

Examples

select rdb$get_context('SYSTEM', 'DB_NAME') from rdb$database

New.UserAddr = rdb$get_context('SYSTEM', 'CLIENT_ADDRESS');

insert into MyTable (TestField)
  values (rdb$get_context('USER_SESSION', 'MyVar'))

See also

[fblangref50-scalarfuncs-set-context]

`RDB$SET_CONTEXT()`

Creates, sets or clears a variable in one of the user-writable namespaces

Result type

INTEGER

Syntax

RDB$SET_CONTEXT ('<namespace>', <varname>, <value> | NULL)

<namespace> ::= USER_SESSION | USER_TRANSACTION
<varname>   ::= A case-sensitive quoted string of max. 80 characters
<value>     ::= A value of any type, as long as it's castable
                to a VARCHAR(255)

Table 1. `RDB$SET_CONTEXT` Function Parameters
Parameter	Description
namespace	Namespace
varname	Variable name.Case-sensitive.Maximum length is 80 characters
value	Data of any type provided it can be cast to `VARCHAR(255)`

The namespaces

The USER_SESSION and USER_TRANSACTION namespaces are initially empty.A user can create and set variables with RDB$SET_CONTEXT() and retrieve them with [fblangref50-scalarfuncs-get-context].The USER_SESSION context is bound to the current connection, the USER_TRANSACTION context to the current transaction.

Lifecycle

When a transaction ends, its USER_TRANSACTION context is cleared.
When a connection is closed, its USER_SESSION context is cleared.
When a connection is reset using ALTER SESSION RESET, the USER_TRANSACTION and USER_SESSION contexts are cleared.

Return values and error behaviour

The function returns 1 when the variable already existed before the call and 0 when it didn’t.To remove a variable from a context, set it to NULL.If the given namespace doesn’t exist, an error is raised.Both namespace and variable names must be entered as single-quoted, case-sensitive, non-NULL strings.

Note

The maximum number of variables in any single context is 1000.
All USER_TRANSACTION variables survive a ROLLBACK RETAIN (see ROLLBACK Options) or ROLLBACK TO SAVEPOINT unaltered, no matter at which point during the transaction they were set.
Due to its UDF-like nature, RDB$SET_CONTEXT can — in PSQL only — be called like a void function, without assigning the result, as in the second example above.Regular internal functions don’t allow this type of use.
ALTER SESSION RESET clears both USER_TRANSACTION and USER_SESSION contexts.

Examples

select rdb$set_context('USER_SESSION', 'MyVar', 493) from rdb$database

rdb$set_context('USER_SESSION', 'RecordsFound', RecCounter);

select rdb$set_context('USER_TRANSACTION', 'Savepoints', 'Yes')
  from rdb$database

See also

[fblangref50-scalarfuncs-get-context]

Special Functions for `DECFLOAT`

`COMPARE_DECFLOAT()`

Compares two DECFLOAT values to be equal, different or unordered

Result type

SMALLINT

Syntax

COMPARE_DECFLOAT (decfloat1, decfloat2)

Table 1. `COMPARE_DECFLOAT` Function Parameters
Parameter	Description
decfloatn	Value or expression of type `DECFLOAT`, or cast-compatible with `DECFLOAT`

The result is a SMALLINT value, as follows:

`0`	Values are equal
`1`	First value is less than second
`2`	First value is greater than second
`3`	Values are unordered, i.e. one or both is `NaN`/`sNaN`

Unlike the comparison operators (‘<’, ‘=’, ‘>’, etc.), comparison is exact: COMPARE_DECFLOAT(2.17, 2.170) returns 2 not 0.

See also

[fblangref50-scalarfuncs-totalorder]

`NORMALIZE_DECFLOAT()`

Returns the simplest, normalized form of a DECFLOAT

Result type

DECFLOAT

Syntax

NORMALIZE_DECFLOAT (decfloat_value)

Table 1. `NORMALIZE_DECFLOAT` Function Parameters
Parameter	Description
decfloat_value	Value or expression of type `DECFLOAT`, or cast-compatible with `DECFLOAT`

For any non-zero value, trailing zeroes are removed with appropriate correction of the exponent.

Examples of `NORMALIZE_DECFLOAT`

-- will return 12
select normalize_decfloat(12.00)
from rdb$database;

-- will return 1.2E+2
select normalize_decfloat(120)
from rdb$database;

`QUANTIZE()`

Returns a value that is equal in value — except for rounding — to the first argument, but with the same exponent as the second argument

Result type

DECFLOAT

Syntax

QUANTIZE (decfloat_value, exp_value)

Table 1. `QUANTIZE` Function Parameters
Parameter	Description
decfloat_value	Value or expression to quantize;needs to be of type `DECFLOAT`, or cast-compatible with `DECFLOAT`
exp_value	Value or expression to use for its exponent;needs to be of type `DECFLOAT`, or cast-compatible with `DECFLOAT`

QUANTIZE returns a DECFLOAT value that is equal in value and sign (except for rounding) to decfloat_value, and that has an exponent equal to the exponent of exp_value.The type of the return value is DECFLOAT(16) if both arguments are DECFLOAT(16), otherwise the result type is DECFLOAT(34).

Note

The target exponent is the exponent used in the Decimal64 or Decimal128 storage format of DECFLOAT of exp_value.This is not necessarily the same as the exponent displayed in tools like isql.For example, the value 1.23E+2 is coefficient 123 and exponent 0, while 1.2 is coefficient 12 and exponent -1.

If the exponent of decfloat_value is greater than the one of exp_value, the coefficient of decfloat_value is multiplied by a power of ten, and its exponent decreased.If the exponent is smaller, then its coefficient is rounded using the current decfloat rounding mode, and its exponent is increased.

When it is not possible to achieve the target exponent because the coefficient would exceed the target precision (16 or 34 decimal digits), either a “Decfloat float invalid operation” error is raised or NaN is returned (depending on the current decfloat traps configuration).

There are almost no restrictions on the exp_value.However, in almost all usages, NaN/sNaN/Infinity will produce an exception (unless allowed by the current decfloat traps configuration), NULL will make the function return NULL, and so on.

Examples of `QUANTIZE`

select v, pic, quantize(v, pic) from examples;

     V    PIC QUANTIZE
====== ====== ========
  3.16  0.001    3.160
  3.16   0.01     3.16
  3.16    0.1      3.2
  3.16      1        3
  3.16   1E+1     0E+1
  -0.1      1       -0
     0   1E+5     0E+5
   316    0.1    316.0
   316      1      316
   316   1E+1   3.2E+2
   316   1E+2     3E+2

`TOTALORDER()`

Determines the total or linear order of its arguments

Result type

SMALLINT

Syntax

TOTALORDER (decfloat1, decfloat2)

Table 1. `TOTALORDER` Function Parameters
Parameter	Description
decfloatn	Value or expression of type `DECFLOAT`, or cast-compatible with `DECFLOAT`

TOTALORDER compares two DECFLOAT values including any special values.The comparison is exact, and returns a SMALLINT, one of:

`-1`	First value is less than second
`0`	Values are equal
`1`	First value is greater than second.

For TOTALORDER comparisons, DECFLOAT values are ordered as follows:

-NaN < -sNaN < -INF < -0.1 < -0.10 < -0 < 0 < 0.10 < 0.1 < INF < sNaN < NaN

Cryptographic Functions

`DECRYPT()`

Decrypts data using a symmetric cipher

Result type

VARBINARY or BLOB

Syntax

DECRYPT ( encrypted_input
  USING <algorithm> [MODE <mode>]
  KEY key
  [IV iv] [<ctr_type>] [CTR_LENGTH ctr_length]
  [COUNTER initial_counter] )

!! See syntax of <<fblangref50-scalarfuncs-encrypt,ENCRYPT>> for further rules !!

Table 1. `DECRYPT` Function Parameters
Parameter	Description
encrypted_input	Encrypted input as a blob or (binary) string
See [fblangref50-scalarfuncs-tbl-encrypt] for other parameters

Note

Sizes of data strings (like encrypted_input, key and iv) must meet the requirements of the selected algorithm and mode.
This function returns BLOB SUB_TYPE BINARY when the first argument is a BLOB, and VARBINARY for all other text and binary types.
When the encrypted data was text, it must be explicitly cast to a string type of appropriate character set.
The ins and outs of the various algorithms are considered beyond the scope of this language reference.We recommend searching the internet for further details on the algorithms.

`DECRYPT` Examples

select decrypt(x'0154090759DF' using sober128 key 'AbcdAbcdAbcdAbcd' iv '01234567')
  from rdb$database;
select decrypt(secret_field using aes mode ofb key '0123456701234567' iv init_vector)
  from secure_table;

`ENCRYPT()`

Encrypts data using a symmetric cipher

Result type

VARBINARY or BLOB

Syntax

ENCRYPT ( input
  USING <algorithm> [MODE <mode>]
  KEY key
  [IV iv] [<ctr_type>] [CTR_LENGTH ctr_length]
  [COUNTER initial_counter] )

<algorithm> ::= <block_cipher> | <stream_cipher>

<block_cipher> ::=
    AES | ANUBIS | BLOWFISH | KHAZAD | RC5
  | RC6 | SAFER+ | TWOFISH | XTEA

<stream_cipher> ::= CHACHA20 | RC4 | SOBER128

<mode> ::= CBC | CFB | CTR | ECB | OFB

<ctr_type> ::= CTR_BIG_ENDIAN | CTR_LITTLE_ENDIAN

Table 1. `ENCRYPT` Function Parameters
Parameter	Description
input	Input to encrypt as a blob or (binary) string
algorithm	The algorithm to use for decryption
mode	The algorithm mode;only for block ciphers
key	The encryption/decryption key
iv	Initialization vector or nonce;should be specified for block ciphers in all modes except `ECB`, and all stream ciphers except `RC4`
ctr_type	Endianness of the counter;only for `CTR` mode.Default is `CTR_LITTLE_ENDIAN`.
ctr_length	Counter length;only for `CTR` mode.Default is size of iv.
initial_counter	Initial counter value;only for `CHACHA20`.Default is `0`.

Note

This function returns BLOB SUB_TYPE BINARY when the first argument is a BLOB, and VARBINARY for all other text and binary types.
Sizes of data strings (like key and iv) must meet the requirements of the selected algorithm and mode, see table [fblangref50-scalarfuncs-tbl-encrypt-req].
- In general, the size of iv must match the block size of the algorithm
- For ECB and CBC mode, input must be multiples of the block size, you will need to manually pad with zeroes or spaces as appropriate.
The ins and outs of the various algorithms and modes are considered beyond the scope of this language reference.We recommend searching the internet for further details on the algorithms.
Although specified as separate options in this Language Reference, in the actual syntax CTR_LENGTH and COUNTER are aliases.

Table 2. Encryption Algorithm Requirements
Algorithm	Key size (bytes)	Block size (bytes)	Notes
Block Ciphers
`AES`	16, 24, 32	16	Key size determines the AES variant: 16 bytes → AES-128 24 bytes → AES-192 32 bytes → AES-256
`ANUBIS`	16 - 40, in steps of 4 (4x)	16
`BLOWFISH`	8 - 56	8
`KHAZAD`	16	8
`RC5`	8 - 128	8
`RC6`	8 - 128	16
`SAFER+`	16, 24, 32	16
`TWOFISH`	16, 24, 32	16
`XTEA`	16	8
Stream Ciphers
`CHACHA20`	16, 32	1	Nonce size (IV) is 8 or 12 bytes.For nonce size 8, initial_counter is a 64-bit integer, for size 12, 32-bit.
`RC4`	5 - 256	1
`SOBER128`	4x	1	Nonce size (IV) is 4y bytes, the length is independent of key size.

`ENCRYPT` Examples

select encrypt('897897' using sober128 key 'AbcdAbcdAbcdAbcd' iv '01234567')
  from rdb$database;

`RSA_DECRYPT()`

Decrypts data using an RSA private key and removes OAEP or PKCS 1.5 padding

Result type

VARBINARY

Syntax

RSA_DECRYPT (encrypted_input KEY private_key
  [LPARAM tag_string] [HASH <hash>] [PKCS_1_5])

<hash> ::= MD5 | SHA1 | SHA256 | SHA512

Table 1. `RSA_DECRYPT` Function Parameters
Parameter	Description
encrypted_input	Input data to decrypt
private_key	Private key to apply, PKCS#1 format
tag_string	An additional system-specific tag to identify which system encrypted the message;default is `NULL`.If the tag does not match what was used during encryption, `RSA_DECRYPT` will not decrypt the data.
hash	The hash used for OAEP padding;default is `SHA256`.

RSA_DECRYPT decrypts encrypted_input using the RSA private key and then removes padding from the resulting data.

By default, OAEP padding is used.The PKCS_1_5 option will switch to the less secure PKCS 1.5 padding.

Warning

The PKCS_1_5 option is only for backward compatibility with systems applying PKCS 1.5 padding.For security reasons, it should not be used in new projects.

Note	This function returns `VARBINARY`. When the encrypted data was text, it must be explicitly cast to a string type of appropriate character set.

`RSA_DECRYPT` Examples

Tip	Run the examples of the `RSA_PRIVATE` and `RSA_PUBLIC`, `RSA_ENCRYPT` functions first.

select cast(rsa_decrypt(rdb$get_context('USER_SESSION', 'msg')
  key rdb$get_context('USER_SESSION', 'private_key')) as varchar(128))
from rdb$database;

`RSA_ENCRYPT()`

Pads data using OAEP or PKCS 1.5 and then encrypts it with an RSA public key

Result type

VARBINARY

Syntax

RSA_ENCRYPT (input KEY public_key
  [LPARAM tag_string] [HASH <hash>] [PKCS_1_5])

<hash> ::= MD5 | SHA1 | SHA256 | SHA512

Table 1. `RSA_ENCRYPT` Function Parameters
Parameter	Description
input	Input data to encrypt
public_key	Public key to apply, PKCS#1 format
tag_string	An additional system-specific tag to identify which system encrypted the message;default is `NULL`.
hash	The hash used for OAEP padding;default is `SHA256`.

RSA_ENCRYPT pads input using the OAEP or PKCS 1.5 padding scheme and then encrypts it using the specified RSA public key.This function is normally used to encrypt short symmetric keys which are then used in block ciphers to encrypt a message.

By default, OAEP padding is used.The PKCS_1_5 option will switch to the less secure PKCS 1.5 padding.

Warning

The PKCS_1_5 option is only for backward compatibility with systems applying PKCS 1.5 padding.For security reasons, it should not be used in new projects.

`RSA_ENCRYPT` Examples

Tip	Run the examples of the `RSA_PRIVATE` and `RSA_PUBLIC` functions first.

select rdb$set_context('USER_SESSION', 'msg', rsa_encrypt('Some message'
  key rdb$get_context('USER_SESSION', 'public_key'))) from rdb$database;

`RSA_PRIVATE()`

Generates an RSA private key

Result type

VARBINARY

Syntax

RSA_PRIVATE (key_length)

Table 1. `RSA_PRIVATE` Function Parameters
Parameter	Description
key_length	Key length in bytes;minimum 4, maximum 1024.A size of 256 bytes (2048 bits) or larger is recommended.

RSA_PRIVATE generates an RSA private key of the specified length (in bytes) in PKCS#1 format.

Note	The larger the length specified, the longer it takes for the function to generate a private key.

`RSA_PRIVATE` Examples

select rdb$set_context('USER_SESSION', 'private_key', rsa_private(256))
  from rdb$database;

Warning

Putting private keys in the context variables is not secure;we’re doing it here for demonstration purposes.SYSDBA and users with the role RDB$ADMIN or the system privilege MONITOR_ANY_ATTACHMENT can see all context variables from all attachments.

`RSA_PUBLIC()`

Generates an RSA public key

Result type

VARBINARY

Syntax

RSA_PUBLIC (private_key)

Table 1. `RSA_PUBLIC` Function Parameters
Parameter	Description
private_key	RSA private key in PKCS#1 format

RSA_PUBLIC returns the RSA public key in PKCS#1 format for the provided RSA private key (also PKCS#1 format).

`RSA_PUBLIC` Examples

Tip	Run the example of the `RSA_PRIVATE` function first.

select rdb$set_context('USER_SESSION', 'public_key',
  rsa_public(rdb$get_context('USER_SESSION', 'private_key'))) from rdb$database;

`RSA_SIGN_HASH()`

PSS encodes a message hash and signs it with an RSA private key

Result type

VARBINARY

Syntax

RSA_SIGN_HASH (message_digest
  KEY private_key
  [HASH <hash>] [SALT_LENGTH salt_length]
  [PKCS_1_5])

<hash> ::= MD5 | SHA1 | SHA256 | SHA512

Table 1. `RSA_SIGN_HASH` Function Parameters
Parameter	Description
message_digest	Hash of message to sign.The hash algorithm used should match hash
private_key	RSA private key in PKCS#1 format
hash	Hash to generate PSS encoding;default is `SHA256`.This should be the same hash as used to generate message_digest.
salt_length	Length of the desired salt in bytes;default is 8;minimum 1, maximum 32.The recommended value is between 8 and 16.

RSA_SIGN_HASH performs PSS encoding of the message_digest to be signed, and signs using the RSA private key.

By default, OAEP padding is used.The PKCS_1_5 option will switch to the less secure PKCS 1.5 padding.

Warning

The PKCS_1_5 option is only for backward compatibility with systems applying PKCS 1.5 padding.For security reasons, it should not be used in new projects.

Caution

This function expects the hash of a message (or message digest), not the actual message.The hash argument should specify the algorithm that was used to generate that hash.

A function that accepts the actual message to hash might be introduced in a future version of Firebird.

PSS encoding

Probabilistic Signature Scheme (PSS) is a cryptographic signature scheme specifically developed to allow modern methods of security analysis to prove that its security directly relates to that of the RSA problem.There is no such proof for the traditional PKCS#1 v1.5 scheme.

`RSA_SIGN_HASH` Examples

Tip	Run the example of the `RSA_PRIVATE` function first.

select rdb$set_context('USER_SESSION', 'msg',
  rsa_sign_hash(crypt_hash('Test message' using sha256)
    key rdb$get_context('USER_SESSION', 'private_key'))) from rdb$database;

`RSA_VERIFY_HASH()`

Verifies a message hash against a signature using an RSA public key

Result type

BOOLEAN

Syntax

RSA_VERIFY_HASH (message_digest
  SIGNATURE signature KEY public_key
  [HASH <hash>] [SALT_LENGTH salt_length]
  [PKCS_1_5])

<hash> ::= MD5 | SHA1 | SHA256 | SHA512

Table 1. `RSA_VERIFY` Function Parameters
Parameter	Description
message_digest	Hash of message to verify.The hash algorithm used should match hash
signature	Expected signature of input generated by `RSA_SIGN_HASH`
public_key	RSA public key in PKCS#1 format matching the private key used to sign
hash	Hash to use for the message digest;default is `SHA256`.This should be the same hash as used to generate message_digest, and as used in `RSA_SIGN_HASH`
salt_length	Length of the salt in bytes;default is 8;minimum 1, maximum 32.Value must match the length used in `RSA_SIGN_HASH`.

RSA_VERIFY_HASH performs PSS encoding of the message_digest to be verified, and verifies the digital signature using the provided RSA public key.

By default, OAEP padding is used.The PKCS_1_5 option will switch to the less secure PKCS 1.5 padding.

Warning

The PKCS_1_5 option is only for backward compatibility with systems applying PKCS 1.5 padding.For security reasons, it should not be used in new projects.

Caution

This function expects the hash of a message (or message digest), not the actual message.The hash argument should specify the algorithm that was used to generate that hash.

A function that accepts the actual message to hash might be introduced in a future version of Firebird.

`RSA_VERIFY_HASH` Examples

Tip	Run the examples of the `RSA_PRIVATE`, `RSA_PUBLIC` and `RSA_SIGN_HASH` functions first.

select rsa_verify_hash(
  crypt_hash('Test message' using sha256)
  signature rdb$get_context('USER_SESSION', 'msg')
  key rdb$get_context('USER_SESSION', 'public_key'))
from rdb$database

Other Functions

Functions that don’t fit in any other category.

`MAKE_DBKEY()`

Creates a DBKEY value

Result type

BINARY(8)

Syntax

MAKE_DBKEY (relation, recnum [, dpnum [, ppnum]])

Table 1. `RDB$GET_TRANSACTION_CN` Function Parameters
Parameter	Description
relation	Relation name or relation id
recnum	Record number.Either absolute (if dpnum and ppnum are absent), or relative (if dpnum present)
dpnum	Data page number.Either absolute (if ppnum is absent) or relative (if ppnum present)
ppnum	Pointer page number.

MAKE_DBKEY creates a DBKEY value using a relation name or ID, record number, and (optionally) logical numbers of data page and pointer page.

Note

If relation is a string expression or literal, then it is treated as a relation name, and the engine searches for the corresponding relation ID.The search is case-sensitive.In the case of string literal, relation ID is evaluated at query preparation time.In the case of expression, relation ID is evaluated at execution time.If the relation cannot be found, then error isc_relnotdef is raised.
If relation is a numeric expression or literal, then it is treated as a relation ID and used “as is”, without verification against existing relations.If the argument value is negative or greater than the maximum allowed relation ID (65535 currently), then NULL is returned.
Argument recnum represents an absolute record number in the relation (if the next arguments dpnum and ppnum are missing), or a record number relative to the first record, specified by the next arguments.
Argument dpnum is a logical number of data page in the relation (if the next argument ppnum is missing), or number of data pages relative to the first data page addressed by the given ppnum.
Argument ppnum is a logical number of pointer page in the relation.
All numbers are zero-based.Maximum allowed value for dpnum and ppnum is 2³² (4294967296).If dpnum is specified, then recnum can be negative.If dpnum is missing and recnum is negative, then NULL is returned.If ppnum is specified, then dpnum can be negative.If ppnum is missing and dpnum is negative, then NULL is returned.
If any of specified arguments is NULL, the result is also NULL.
Argument relation is described as INTEGER during query preparation, but it can be overridden by a client application as VARCHAR or CHAR.Arguments recnum, dpnum and ppnum are described as BIGINT.

Examples of `MAKE_DBKEY`

Select record using relation name (note that relation name is uppercase)

select *
from rdb$relations
where rdb$db_key = make_dbkey('RDB$RELATIONS', 0)

Select record using relation ID

select *
from rdb$relations
where rdb$db_key = make_dbkey(6, 0)

Select all records physically residing on the first data page

select *
from rdb$relations
where rdb$db_key >= make_dbkey(6, 0, 0)
and rdb$db_key < make_dbkey(6, 0, 1)

Select all records physically residing on the first data page of 6th pointer page

select *
from SOMETABLE
where rdb$db_key >= make_dbkey('SOMETABLE', 0, 0, 5)
and rdb$db_key < make_dbkey('SOMETABLE', 0, 1, 5)

`RDB$ERROR()`

Returns PSQL error information inside a WHEN … DO block

Available in

PSQL

Result type

Varies (see table below)

Syntax

RDB$ERROR (<context>)

<context> ::=
  GDSCODE | SQLCODE | SQLSTATE | EXCEPTION | MESSAGE

Table 1. Contexts
Context	Result type	Description
`GDSCODE`	`INTEGER`	Firebird error code, see also `GDSCODE`
`SQLCODE`	`INTEGER`	(deprecated) SQL code, see also `SQLCODE`
`SQLSTATE`	`CHAR(5) CHARACTER SET ASCII`	SQLstate, see also `SQLSTATE`
`EXCEPTION`	`VARCHAR(63) CHARACTER SET UTF8`	Name of the active user-defined exception or `NULL` if the active exception is a system exception
`MESSAGE`	`VARCHAR(1024) CHARACTER SET UTF8`	Message text of the active exception

RDB$ERROR returns data of the specified context about the active PSQL exception.Its scope is confined to exception-handling blocks in PSQL (WHEN … DO).Outside the exception handling blocks, RDB$ERROR always returns NULL.This function cannot be called from DSQL.

Example of RDB$ERROR

BEGIN
  ...
WHEN ANY DO
  EXECUTE PROCEDURE P_LOG_EXCEPTION(RDB$ERROR(MESSAGE));
END

`RDB$GET_TRANSACTION_CN()`

Returns the commit number (“CN”) of a transaction

Result type

BIGINT

Syntax

RDB$GET_TRANSACTION_CN (transaction_id)

Table 1. `RDB$GET_TRANSACTION_CN` Function Parameters
Parameter	Description
transaction_id	Transaction id

If the return value is greater than 1, it is the actual CN of the transaction if it was committed after the database was started.

The function can also return one of the following results, indicating the commit status of the transaction:

`-2`	Transaction is dead (rolled back)
`-1`	Transaction is in limbo
`0`	Transaction is still active
`1`	Transaction committed before the database started or less than the Oldest Interesting Transaction for the database
`NULL`	Transaction number supplied is NULL or greater than Next Transaction for the database

Note	For more information about CN, consult theFirebird 4.0 Release Notes.

`RDB$GET_TRANSACTION_CN` Examples

select rdb$get_transaction_cn(current_transaction) from rdb$database;
select rdb$get_transaction_cn(123) from rdb$database;

`RDB$ROLE_IN_USE()`

Checks if a role is active for the current connection

Result type

BOOLEAN

Syntax

RDB$ROLE_IN_USE (role_name)

Table 1. `RDB$ROLE_IN_USE` Function Parameters
Parameter	Description
role_name	String expression for the role to check.Case-sensitive, must match the role name as stored in `RDB$ROLES`

RDB$ROLE_IN_USE returns TRUE if the specified role is active for the current connection, and FALSE otherwise.Contrary to CURRENT_ROLE — which only returns the explicitly specified role — this function can be used to check for roles that are active by default, or cumulative roles activated by an explicitly specified role.

`RDB$ROLE_IN_USE` Examples

List currently active roles

select rdb$role_name
from rdb$roles
where rdb$role_in_use(rdb$role_name);

See also

CURRENT_ROLE

`RDB$SYSTEM_PRIVILEGE()`

Checks if the authorization of the current connection has a system privilege

Result type

BOOLEAN

Syntax

RDB$SYSTEM_PRIVILEGE (<sys_privilege>)

<sys_privilege> ::=
  !! See CREATE ROLE !!

Table 1. `RDB$SYSTEM_PRIVILEGE` Function Parameters
Parameter	Description
sys_privilege	System privilege

RDB$SYSTEM_PRIVILEGE accepts a system privilege name and returns TRUE if the current connection has the given system privilege, and FALSE otherwise.

The authorization of the current connection is determined by privileges of the current user, the user PUBLIC, and the currently active roles (explicitly set or activated by default).

`RDB$SYSTEM_PRIVILEGE` Examples

select rdb$system_privilege(user_management) from rdb$database;

See also

Fine-grained System Privileges

Mathematical Functions

`ABS()`

Absolute value

Result type

Numerical, matching input type

Syntax

ABS (number)

Table 1. `ABS` Function Parameter
Parameter	Description
number	An expression of a numeric type

`COS()`

Cosine

Result type

DOUBLE PRECISION

Syntax

COS (angle)

Table 1. `COS` Function Parameter
Parameter	Description
angle	An angle in radians

The result is in the range [-1, 1].

`COSH()`

Hyperbolic cosine

Result type

DOUBLE PRECISION

Syntax

COSH (number)

Table 1. `COSH` Function Parameter
Parameter	Description
number	A number of a numeric type

The result is in the range [1, INF].

`COT()`

Cotangent

Result type

DOUBLE PRECISION

Syntax

COT (angle)

Table 1. `COT` Function Parameter
Parameter	Description
angle	An angle in radians

`EXP()`

Natural exponent

Result type

DOUBLE PRECISION

Syntax

EXP (number)

Table 1. `EXP` Function Parameter
Parameter	Description
number	A number of a numeric type

Returns the natural exponential, e^number

See also

[fblangref50-scalarfuncs-ln]

`FLOOR()`

Floor of a number

Result type

BIGINT or INT128 for exact numeric number, or DOUBLE PRECISION or DECFLOAT for floating point number

Syntax

FLOOR (number)

Table 1. `FLOOR` Function Parameter
Parameter	Description
number	An expression of a numeric type

Returns the largest whole number smaller than or equal to the argument.

`LN()`

Natural logarithm

Result type

DOUBLE PRECISION

Syntax

LN (number)

Table 1. `LN` Function Parameter
Parameter	Description
number	An expression of a numeric type

An error is raised if the argument is negative or 0.

`LOG()`

Logarithm with variable base

Result type

DOUBLE PRECISION

Syntax

LOG (x, y)

Table 1. `LOG` Function Parameters
Parameter	Description
x	Base.An expression of a numeric type
y	An expression of a numeric type

Returns the x-based logarithm of y.

If either argument is 0 or below, an error is raised.
If both arguments are 1, NaN is returned.
If x = 1 and y < 1, -INF is returned.
If x = 1 and y > 1, INF is returned.

`LOG10()`

Decimal (base-10) logarithm

Result type

DOUBLE PRECISION

Syntax

LOG10 (number)

Table 1. `LOG10` Function Parameter
Parameter	Description
number	An expression of a numeric type

An error is raised if the argument is negative or 0.

`MOD()`

Remainder

Result type

SMALLINT, INTEGER or BIGINT depending on the type of a.If a is a floating-point type, the result is a BIGINT.

Syntax

MOD (a, b)

Table 1. `MOD` Function Parameters
Parameter	Description
a	An expression of a numeric type
b	An expression of a numeric type

Returns the remainder of an integer division.

Non-integer arguments are rounded before the division takes place.So, “mod(7.5, 2.5)” gives 2 (“mod(8, 3)”), not 0.
Do not confuse MOD() with the mathematical modulus operator;e.g. mathematically, -21 mod 4 is 3, while Firebird’s MOD(-21, 4) is -1.In other words, MOD() behaves as % in languages like C and Java.

`PI()`

Approximation of pi.

Result type

DOUBLE PRECISION

Syntax

PI ()

`ACOS()`

Arc cosine

Result type

DOUBLE PRECISION

Syntax

ACOS (number)

Table 1. `ACOS` Function Parameter
Parameter	Description
number	An expression of a numeric type within the range [-1, 1]

The result is an angle in the range [0, pi].

`POWER()`

Power

Result type

DOUBLE PRECISION

Syntax

POWER (x, y)

Table 1. `POWER` Function Parameters
Parameter	Description
x	An expression of a numeric type
y	An expression of a numeric type

Returns x to the power of y (x^y).

`RAND()`

Generates a random number

Result type

DOUBLE PRECISION

Syntax

RAND ()

Returns a random number between 0 and 1.

`ROUND()`

Result type

single argument: integer type, DOUBLE PRECISION or DECFLOAT;
two arguments: numerical, matching first argument

Syntax

ROUND (number [, scale])

Table 1. `ROUND` Function Parameters
Parameter	Description
number	An expression of a numeric type
scale	An integer specifying the number of decimal places toward which rounding is to be performed, e.g.: 2 for rounding to the nearest multiple of 0.01 1 for rounding to the nearest multiple of 0.1 0 for rounding to the nearest whole number -1 for rounding to the nearest multiple of 10 -2 for rounding to the nearest multiple of 100

Rounds a number to the nearest integer.If the fractional part is exactly 0.5, rounding is upward for positive numbers and downward for negative numbers.With the optional scale argument, the number can be rounded to powers-of-ten multiples (tens, hundreds, tenths, hundredths, etc.).

Important

If you are used to the behaviour of the external function ROUND, please notice that the internal function always rounds halves away from zero, i.e. downward for negative numbers.

`ROUND` Examples

If the scale argument is present, the result usually has the same scale as the first argument:

ROUND(123.654, 1) -- returns 123.700 (not 123.7)
ROUND(8341.7, -3) -- returns 8000.0 (not 8000)
ROUND(45.1212, 0) -- returns 45.0000 (not 45)

Otherwise, the result scale is 0:

ROUND(45.1212) -- returns 45

`SIGN()`

Sign or signum

Result type

SMALLINT

Syntax

SIGN (number)

Table 1. `SIGN` Function Parameter
Parameter	Description
number	An expression of a numeric type

Returns the sign of the argument: -1, 0 or 1

number < 0 → -1
number = 0 → 0
number > 0 → 1

`SIN()`

Sine

Result type

DOUBLE PRECISION

Syntax

SIN (angle)

Table 1. `SIN` Function Parameter
Parameter	Description
angle	An angle, in radians

The result is in the range [-1, 1].

`SINH()`

Hyperbolic sine

Result type

DOUBLE PRECISION

Syntax

SINH (number)

Table 1. `SINH` Function Parameter
Parameter	Description
number	An expression of a numeric type

`SQRT()`

Square root

Result type

DOUBLE PRECISION

Syntax

SQRT (number)

Table 1. `SQRT` Function Parameter
Parameter	Description
number	An expression of a numeric type

If number is negative, an error is raised.

See also

[fblangref50-scalarfuncs-power]

`TAN()`

Tangent

Result type

DOUBLE PRECISION

Syntax

TAN (angle)

Table 1. `TAN` Function Parameter
Parameter	Description
angle	An angle, in radians

`TANH()`

Hyperbolic tangent

Result type

DOUBLE PRECISION

Syntax

TANH (number)

Table 1. `TANH` Function Parameters
Parameter	Description
number	An expression of a numeric type

Due to rounding, the result is in the range [-1, 1] (mathematically, it’s <-1, 1>).

`TRUNC()`

Truncate number

Result type

single argument: integer type, DOUBLE PRECISION or DECFLOAT;
two arguments: numerical, matching first argument

Syntax

TRUNC (number [, scale])

Table 1. `TRUNC` Function Parameters
Parameter	Description
number	An expression of a numeric type
scale	An integer specifying the number of decimal places toward which truncating is to be performed, e.g.: 2 for truncating to the nearest multiple of 0.01 1 for truncating to the nearest multiple of 0.1 0 for truncating to the nearest whole number -1 for truncating to the nearest multiple of 10 -2 for truncating to the nearest multiple of 100

The single argument variant returns the integer part of a number.With the optional scale argument, the number can be truncated to powers-of-ten multiples (tens, hundreds, tenths, hundredths, etc.).

Note

If the scale argument is present, the result usually has the same scale as the first argument, e.g.
- TRUNC(789.2225, 2) returns 789.2200 (not 789.22)
- TRUNC(345.4, -2) returns 300.0 (not 300)
- TRUNC(-163.41, 0) returns -163.00 (not -163)
Otherwise, the result scale is 0:
- TRUNC(-163.41) returns -163

Important

If you are used to the behaviour of the external function TRUNCATE, please notice that the internal function TRUNC always truncates toward zero, i.e. upward for negative numbers.

`ACOSH()`

Inverse hyperbolic cosine

Result type

DOUBLE PRECISION

Syntax

ACOSH (number)

Table 1. `ACOSH` Function Parameter
Parameter	Description
number	Any non-`NULL` value in the range [1, INF].

The result is in the range [0, INF].

`ASIN()`

Arc sine

Result type

DOUBLE PRECISION

Syntax

ASIN (number)

Table 1. `ASIN` Function Parameter
Parameter	Description
number	An expression of a numeric type within the range [-1, 1]

The result is an angle in the range [-pi/2, pi/2].

`ASINH()`

Inverse hyperbolic sine

Result type

DOUBLE PRECISION

Syntax

ASINH (number)

Table 1. `ASINH` Function Parameter
Parameter	Description
number	Any non-`NULL` value in the range [-INF, INF].

The result is in the range [-INF, INF].

`ATAN()`

Arc tangent

Result type

DOUBLE PRECISION

Syntax

ATAN (number)

Table 1. `ATAN` Function Parameter
Parameter	Description
number	An expression of a numeric type

The result is an angle in the range <-pi/2, pi/2>.

`ATAN2()`

Two-argument arc tangent

Result type

DOUBLE PRECISION

Syntax

ATAN2 (y, x)

Table 1. `ATAN2` Function Parameters
Parameter	Description
y	An expression of a numeric type
x	An expression of a numeric type

Returns the angle whose sine-to-cosine ratio is given by the two arguments, and whose sine and cosine signs correspond to the signs of the arguments.This allows results across the entire circle, including the angles -pi/2 and pi/2.

The result is an angle in the range [-pi, pi].
If x is negative, the result is pi if y is 0, and -pi if y is -0.
If both y and x are 0, the result is meaningless.An error will be raised if both arguments are 0.

A fully equivalent description of this function is the following: ATAN2(y, x) is the angle between the positive X-axis and the line from the origin to the point (x, y).This also makes it obvious that ATAN2(0, 0) is undefined.
If x is greater than 0, ATAN2(y, x) is the same as ATAN(y/x).
If both sine and cosine of the angle are already known, ATAN2(sin, cos) gives the angle.

`ATANH()`

Inverse hyperbolic tangent

Result type

DOUBLE PRECISION

Syntax

ATANH (number)

Table 1. `ATANH` Function Parameter
Parameter	Description
number	Any non-`NULL` value in the range <-1, 1>.

The result is a number in the range [-INF, INF].

`CEIL()`, `CEILING()`

Ceiling of a number

Result type

BIGINT or INT128 for exact numeric number, or DOUBLE PRECISION or DECFLOAT for floating point number

Syntax

CEIL[ING] (number)

Table 1. `CEIL[ING]` Function Parameters
Parameter	Description
number	An expression of a numeric type

Returns the smallest whole number greater than or equal to the argument.

String and Binary Functions

`ASCII_CHAR()`

Character from ASCII code

Result type

CHAR(1) CHARACTER SET NONE

Syntax

ASCII_CHAR (code)

Table 1. `ASCII_CHAR` Function Parameter
Parameter	Description
code	An integer within the range from 0 to 255

Returns the ASCII character corresponding to the number passed in the argument.

Important

If you are used to the behaviour of the ASCII_CHAR UDF, which returns an empty string if the argument is 0, please notice that the internal function returns a character with ASCII code 0 (character NUL) here.

`HEX_DECODE()`

Decode a hexadecimal string to binary

Result type

VARBINARY or BLOB

Syntax

HEX_DECODE (hex_data)

Table 1. `HEX_DECODE` Function Parameter
Parameter	Description
hex_data	Hex encoded data

HEX_DECODE decodes a string with hex-encoded data, and returns the decoded value as VARBINARY or BLOB as appropriate for the input.If the length of the type of hex_data is not a multiple of 2, an error is raised at prepare time.If the length of the value of hex_data is not a multiple of 2, an error is raised at execution time.

When the input is not BLOB, the length of the resulting type is calculated as type_length / 2, where type_length is the maximum length in characters of the input type.

Example of `HEX_DECODE`

select cast(hex_decode('48657861646563696D616C') as varchar(12))
from rdb$database;

CAST
============
Hexadecimal

`HEX_ENCODE()`

Encodes a (binary) value to a hexadecimal string

Result type

VARCHAR CHARACTER SET ASCII or BLOB SUB_TYPE TEXT CHARACTER SET ASCII

Syntax

HEX_ENCODE (binary_data)

Table 1. `HEX_ENCODE` Function Parameter
Parameter	Description
binary_data	Binary data (or otherwise convertible to binary) to encode

HEX_ENCODE encodes binary_data with hex, and returns the encoded value as a VARCHAR CHARACTER SET ASCII or BLOB SUB_TYPE TEXT CHARACTER SET ASCII as appropriate for the input.

When the input is not BLOB, the length of the resulting type is calculated as type_length * 2, where type_length is the maximum length in bytes of the input type.If this length exceeds the maximum length of VARCHAR, the function returns a BLOB.

Example of `HEX_ENCODE`

select hex_encode('Hexadecimal')
from rdb$database;

HEX_ENCODE
======================
48657861646563696D616C

`LEFT()`

Extracts the leftmost part of a string

Result type

VARCHAR or BLOB

Syntax

LEFT (string, length)

Table 1. `LEFT` Function Parameters
Parameter	Description
string	An expression of a string type
length	Integer expression.The number of characters to return

This function fully supports text BLOBs of any length, including those with a multi-byte character set.
If string is a BLOB, the result is a BLOB.Otherwise, the result is a VARCHAR(n) with n the length of the input string.
If the length argument exceeds the string length, the input string is returned unchanged.
If the length argument is not a whole number, bankers' rounding (round-to-even) is applied, i.e. 0.5 becomes 0, 1.5 becomes 2, 2.5 becomes 2, 3.5 becomes 4, etc.

See also

[fblangref50-scalarfuncs-right]

`LOWER()`

Converts a string to lowercase

Result type

(VAR)CHAR, (VAR)BINARY or BLOB

Syntax

LOWER (string)

Table 1. `LOWER` Function ParameterS
Parameter	Description
string	An expression of a string type

Returns the lowercase equivalent of the input string.The exact result depends on the character set.With ASCII or NONE for instance, only ASCII characters are lowercased;with character set OCTETS/(VAR)BINARY, the entire string is returned unchanged.

`LOWER` Examples

select Sheriff from Towns
  where lower(Name) = 'cooper''s valley'

See also

[fblangref50-scalarfuncs-upper]

`LPAD()`

Left-pads a string

Result type

VARCHAR or BLOB

Syntax

LPAD (str, endlen [, padstr])

Table 1. `LPAD` Function Parameters
Parameter	Description
str	An expression of a string type
endlen	Output string length
padstr	The character or string to be used to pad the source string up to the specified length.Default is space (“`' '`”)

Left-pads a string with spaces or with a user-supplied string until a given length is reached.

This function fully supports text BLOBs of any length and character set.
If str is a BLOB, the result is a BLOB.Otherwise, the result is a VARCHAR(endlen).
If padstr is given and equal to '' (empty string), no padding takes place.
If endlen is less than the current string length, the string is truncated to endlen, even if padstr is the empty string.

Warning

When used on a BLOB, this function may need to load the entire object into memory.Although it does try to limit memory consumption, this may affect performance if huge BLOBs are involved.

`LPAD` Examples

lpad ('Hello', 12)               -- returns '       Hello'
lpad ('Hello', 12, '-')          -- returns '-------Hello'
lpad ('Hello', 12, '')           -- returns 'Hello'
lpad ('Hello', 12, 'abc')        -- returns 'abcabcaHello'
lpad ('Hello', 12, 'abcdefghij') -- returns 'abcdefgHello'
lpad ('Hello', 2)                -- returns 'He'
lpad ('Hello', 2, '-')           -- returns 'He'
lpad ('Hello', 2, '')            -- returns 'He'

See also

[fblangref50-scalarfuncs-rpad]

`OCTET_LENGTH()`

Length in bytes (octets) of a string or binary value

Result type

INTEGER, or BIGINT for BLOB

Syntax

OCTET_LENGTH (string)

Table 1. `OCTET_LENGTH` Function Parameter
Parameter	Description
string	An expression of a string type

Gives the length in bytes (octets) of the input string.For multi-byte character sets, this may be less than the number of characters times the “formal” number of bytes per character as found in RDB$CHARACTER_SETS.

Note

With arguments of type CHAR or BINARY, this function takes the entire formal string length (i.e. the declared length of a field or variable) into account.If you want to obtain the “logical” byte length, not counting the trailing spaces, right-TRIM the argument before passing it to OCTET_LENGTH.

`OCTET_LENGTH` Examples

select octet_length('Hello!') from rdb$database
-- returns 6

select octet_length(_iso8859_1 'Grüß di!') from rdb$database
-- returns 8: ü and ß take up one byte each in ISO8859_1

select octet_length
  (cast (_iso8859_1 'Grüß di!' as varchar(24) character set utf8))
from rdb$database
-- returns 10: ü and ß take up two bytes each in UTF8

select octet_length
  (cast (_iso8859_1 'Grüß di!' as char(24) character set utf8))
from rdb$database
-- returns 26: all 24 CHAR positions count, and two of them are 2-byte

`OVERLAY()`

Overwrites part of, or inserts into, a string

Result type

VARCHAR or BLOB

Syntax

OVERLAY (string PLACING replacement FROM pos [FOR length])

Table 1. `OVERLAY` Function Parameters
Parameter	Description
string	The string into which the replacement takes place
replacement	Replacement string
pos	The position from which replacement takes place (starting position)
length	The number of characters that are to be overwritten

By default, the number of characters removed from (overwritten in) the host string equals the length of the replacement string.With the optional fourth argument, a different number of characters can be specified for removal.

This function supports BLOBs of any length.
If string or replacement is a BLOB, the result is a BLOB.Otherwise, the result is a VARCHAR(n) with n the sum of the lengths of string and replacement.
As usual in SQL string functions, pos is 1-based.
If pos is beyond the end of string, replacement is placed directly after string.
If the number of characters from pos to the end of string is smaller than the length of replacement (or than the length argument, if present), string is truncated at pos and replacement placed after it.
The effect of a “FOR 0” clause is that replacement is inserted into string.
If any argument is NULL, the result is NULL.
If pos or length is not a whole number, bankers' rounding (round-to-even) is applied, i.e. 0.5 becomes 0, 1.5 becomes 2, 2.5 becomes 2, 3.5 becomes 4, etc.

Warning

When used on a BLOB, this function may need to load the entire object into memory.This may affect performance if huge BLOBs are involved.

`OVERLAY` Examples

overlay ('Goodbye' placing 'Hello' from 2)   -- returns 'GHelloe'
overlay ('Goodbye' placing 'Hello' from 5)   -- returns 'GoodHello'
overlay ('Goodbye' placing 'Hello' from 8)   -- returns 'GoodbyeHello'
overlay ('Goodbye' placing 'Hello' from 20)  -- returns 'GoodbyeHello'

overlay ('Goodbye' placing 'Hello' from 2 for 0) -- r. 'GHellooodbye'
overlay ('Goodbye' placing 'Hello' from 2 for 3) -- r. 'GHellobye'
overlay ('Goodbye' placing 'Hello' from 2 for 6) -- r. 'GHello'
overlay ('Goodbye' placing 'Hello' from 2 for 9) -- r. 'GHello'

overlay ('Goodbye' placing '' from 4)        -- returns 'Goodbye'
overlay ('Goodbye' placing '' from 4 for 3)  -- returns 'Gooe'
overlay ('Goodbye' placing '' from 4 for 20) -- returns 'Goo'

overlay ('' placing 'Hello' from 4)          -- returns 'Hello'
overlay ('' placing 'Hello' from 4 for 0)    -- returns 'Hello'
overlay ('' placing 'Hello' from 4 for 20)   -- returns 'Hello'

See also

[fblangref50-scalarfuncs-replace]

`POSITION()`

Finds the position of the first or next occurrence of a substring in a string

Result type

INTEGER

Syntax

  POSITION (substr IN string)
| POSITION (substr, string [, startpos])

Table 1. `POSITION` Function Parameters
Parameter	Description
substr	The substring whose position is to be searched for
string	The string which is to be searched
startpos	The position in string where the search is to start

Returns the (1-based) position of the first occurrence of a substring in a host string.With the optional third argument, the search starts at a given offset, disregarding any matches that may occur earlier in the string.If no match is found, the result is 0.

Note

The optional third argument is only supported in the second syntax (comma syntax).
The empty string is considered a substring of every string.Therefore, if substr is '' (empty string) and string is not NULL, the result is:
- 1 if startpos is not given;
- startpos if startpos lies within string;
- 0 if startpos lies beyond the end of string.
This function fully supports text BLOBs of any size and character set.

Warning

When used on a BLOB, this function may need to load the entire object into memory.This may affect performance if huge BLOBs are involved.

`POSITION` Examples

position ('be' in 'To be or not to be')   -- returns 4
position ('be', 'To be or not to be')     -- returns 4
position ('be', 'To be or not to be', 4)  -- returns 4
position ('be', 'To be or not to be', 8)  -- returns 17
position ('be', 'To be or not to be', 18) -- returns 0
position ('be' in 'Alas, poor Yorick!')   -- returns 0

See also

[fblangref50-scalarfuncs-substring]

`REPLACE()`

Replaces all occurrences of a substring in a string

Result type

VARCHAR or BLOB

Syntax

REPLACE (str, find, repl)

Table 1. `REPLACE` Function Parameters
Parameter	Description
str	The string in which the replacement is to take place
find	The string to search for
repl	The replacement string

This function fully supports text BLOBs of any length and character set.
If any argument is a BLOB, the result is a BLOB.Otherwise, the result is a VARCHAR(n) with n calculated from the lengths of str, find and repl in such a way that even the maximum possible number of replacements won’t overflow the field.
If find is the empty string, str is returned unchanged.
If repl is the empty string, all occurrences of find are deleted from str.
If any argument is NULL, the result is always NULL, even if nothing would have been replaced.

Warning

When used on a BLOB, this function may need to load the entire object into memory.This may affect performance if huge BLOBs are involved.

`REPLACE` Examples

replace ('Billy Wilder',  'il', 'oog') -- returns 'Boogly Woogder'
replace ('Billy Wilder',  'il',    '') -- returns 'Bly Wder'
replace ('Billy Wilder',  null, 'oog') -- returns NULL
replace ('Billy Wilder',  'il',  null) -- returns NULL
replace ('Billy Wilder', 'xyz',  null) -- returns NULL (!)
replace ('Billy Wilder', 'xyz', 'abc') -- returns 'Billy Wilder'
replace ('Billy Wilder',    '', 'abc') -- returns 'Billy Wilder'

`REVERSE()`

Reverses a string

Result type

VARCHAR

Syntax

REVERSE (string)

Table 1. `REVERSE` Function Parameter
Parameter	Description
string	An expression of a string type

`REVERSE` Examples

reverse ('spoonful')            -- returns 'lufnoops'
reverse ('Was it a cat I saw?') -- returns '?was I tac a ti saW'

Tip	This function is useful if you want to group, search or order on string endings, e.g. when dealing with domain names or email addresses: `create index ix_people_email on people computed by (reverse(email)); select * from people where reverse(email) starting with reverse('.br');`

`ASCII_VAL()`

ASCII code from string

Result type

SMALLINT

Syntax

ASCII_VAL (ch)

Table 1. `ASCII_VAL` Function Parameter
Parameter	Description
ch	A string of the `[VAR]CHAR` data type or a text `BLOB` with the maximum size of 32,767 bytes

Returns the ASCII code of the character passed in.

If the argument is a string with more than one character, the ASCII code of the first character is returned.
If the argument is an empty string, 0 is returned.
If the argument is NULL, NULL is returned.
If the first character of the argument string is multi-byte, an error is raised.

`RIGHT()`

Extracts the rightmost part of a string

Result type

VARCHAR or BLOB

Syntax

RIGHT (string, length)

Table 1. `RIGHT` Function Parameters
Parameter	Description
string	An expression of a string type
length	Integer.The number of characters to return

This function supports text BLOBs of any length.
If string is a BLOB, the result is a BLOB.Otherwise, the result is a VARCHAR(n) with n the length of the input string.
If the length argument exceeds the string length, the input string is returned unchanged.
If the length argument is not a whole number, bankers' rounding (round-to-even) is applied, i.e. 0.5 becomes 0, 1.5 becomes 2, 2.5 becomes 2, 3.5 becomes 4, etc.

Warning

When used on a BLOB, this function may need to load the entire object into memory.This may affect performance if huge BLOBs are involved.

`RPAD()`

Right-pads a string

Result type

VARCHAR or BLOB

Syntax

RPAD (str, endlen [, padstr])

Table 1. `RPAD` Function Parameters
Parameter	Description
str	An expression of a string type
endlen	Output string length
endlen	The character or string to be used to pad the source string up to the specified length.Default is space (`' '`)

Right-pads a string with spaces or with a user-supplied string until a given length is reached.

This function fully supports text BLOBs of any length and character set.
If str is a BLOB, the result is a BLOB.Otherwise, the result is a VARCHAR(endlen).
If padstr is given and equals '' (empty string), no padding takes place.
If endlen is less than the current string length, the string is truncated to endlen, even if padstr is the empty string.

Warning

When used on a BLOB, this function may need to load the entire object into memory.Although it does try to limit memory consumption, this may affect performance if huge BLOBs are involved.

`RPAD` Examples

rpad ('Hello', 12)               -- returns 'Hello       '
rpad ('Hello', 12, '-')          -- returns 'Hello-------'
rpad ('Hello', 12, '')           -- returns 'Hello'
rpad ('Hello', 12, 'abc')        -- returns 'Helloabcabca'
rpad ('Hello', 12, 'abcdefghij') -- returns 'Helloabcdefg'
rpad ('Hello', 2)                -- returns 'He'
rpad ('Hello', 2, '-')           -- returns 'He'
rpad ('Hello', 2, '')            -- returns 'He'

See also

[fblangref50-scalarfuncs-lpad]

`SUBSTRING()`

Extracts a substring by position and length, or by SQL regular expression

Result types

VARCHAR or BLOB

Syntax

SUBSTRING ( <substring-args> )

<substring-args> ::=
    str FROM startpos [FOR length]
  | str SIMILAR <similar-pattern> ESCAPE <escape>

<similar-pattern> ::=
  <similar-pattern-R1>
  <escape> " <similar-pattern-R2> <escape> "
  <similar-pattern-R3>

Table 1. `SUBSTRING` Function Parameters
Parameter	Description
str	An expression of a string type
startpos	Integer expression, the position from which to start retrieving the substring
length	The number of characters to retrieve after the startpos
similar-pattern	SQL regular expression pattern to search for the substring
escape	Escape character

Returns a string’s substring starting at the given position, either to the end of the string or with a given length, or extracts a substring using an SQL regular expression pattern.

If any argument is NULL, the result is also NULL.

Warning

When used on a BLOB, this function may need to load the entire object into memory.Although it does try to limit memory consumption, this may affect performance if huge BLOBs are involved.

Positional `SUBSTRING`

In its simple, positional form (with FROM), this function returns the substring starting at character position startpos (the first character being 1).Without the FOR argument, it returns all the remaining characters in the string.With FOR, it returns length characters or the remainder of the string, whichever is shorter.

When startpos is smaller than 1, substring behaves as if the string has 1 - startpos extra positions before the actual first character at position 1.The length is considered from this imaginary start of the string, so the resulting string could be shorter than the specified length, or even empty.

The function fully supports binary and text BLOBs of any length, and with any character set.If str is a BLOB, the result is also a BLOB.For any other argument type, the result is a VARCHAR.

For non-BLOB arguments, the width of the result field is always equal to the length of str, regardless of startpos and length.So, substring('pinhead' from 4 for 2) will return a VARCHAR(7) containing the string 'he'.

Example

insert into AbbrNames(AbbrName)
  select substring(LongName from 1 for 3) from LongNames;

select substring('abcdef' from 1 for 2) from rdb$database;
-- result: 'ab'

select substring('abcdef' from 2) from rdb$database;
-- result: 'bcdef'

select substring('abcdef' from 0 for 2) from rdb$database;
-- result: 'a'
-- and NOT 'ab', because there is "nothing" at position 0

select substring('abcdef' from -5 for 2) from rdb$database;
-- result: ''
-- length ends before the actual start of the string

Regular Expression `SUBSTRING`

In the regular expression form (with SIMILAR), the SUBSTRING function returns part of the string matching an SQL regular expression pattern.If no match is found, NULL is returned.

The SIMILAR pattern is formed from three SQL regular expression patterns, R1, R2 and R3.The entire pattern takes the form of R1 || '<escape>"' || R2 || '<escape>"' || R3, where <escape> is the escape character defined in the ESCAPE clause.R2 is the pattern that matches the substring to extract, and is enclosed between escaped double quotes (<escape>", e.g. “#"” with escape character ‘#’).R1 matches the prefix of the string, and R3 the suffix of the string.Both R1 and R3 are optional (they can be empty), but the pattern must match the entire string.In other words, it is not sufficient to specify a pattern that only finds the substring to extract.

Tip	The escaped double quotes around R2 can be compared to defining a single capture group in more common regular expression syntax like PCRE.That is, the full pattern is equivalent to `R1(R2)R3`, which must match the entire input string, and the capture group is the substring to be returned.

Note	If any one of R1, R2, or R3 is not a zero-length string and does not have the format of an SQL regular expression, then an exception is raised.

The full SQL regular expression format is described in Syntax: SQL Regular Expressions

Examples

substring('abcabc' similar 'a#"bcab#"c' escape '#')  -- bcab
substring('abcabc' similar 'a#"%#"c' escape '#')     -- bcab
substring('abcabc' similar '_#"%#"_' escape '#')     -- bcab
substring('abcabc' similar '#"(abc)*#"' escape '#')  -- abcabc
substring('abcabc' similar '#"abc#"' escape '#')     -- <null>

`TRIM()`

Trims leading and/or trailing spaces or other substrings from a string

Result type

VARCHAR or BLOB

Syntax

TRIM ([<adjust>] str)

<adjust> ::=  {[<where>] [what]} FROM

<where> ::=  BOTH | LEADING | TRAILING

Table 1. `TRIM` Function Parameters
Parameter	Description
str	An expression of a string type
where	The position the substring is to be removed from — `BOTH` \| `LEADING` \| `TRAILING`.`BOTH` is the default
what	The substring that should be removed (multiple times if there are several matches) from the beginning, the end, or both sides of the input string str.By default, it is space (`' '`)

Removes leading and/or trailing spaces (or optionally other strings) from the input string.

Note	If str is a `BLOB`, the result is a `BLOB`.Otherwise, it is a `VARCHAR(n)` with n the formal length of str.

Warning

When used on a BLOB, this function may need to load the entire object into memory.This may affect performance if huge BLOBs are involved.

`TRIM` Examples

select trim ('  Waste no space   ') from rdb$database
-- returns 'Waste no space'

select trim (leading from '  Waste no space   ') from rdb$database
-- returns 'Waste no space   '

select trim (leading '.' from '  Waste no space   ') from rdb$database
-- returns '  Waste no space   '

select trim (trailing '!' from 'Help!!!!') from rdb$database
-- returns 'Help'

select trim ('la' from 'lalala I love you Ella') from rdb$database
-- returns ' I love you El'

select trim ('la' from 'Lalala I love you Ella') from rdb$database
-- returns 'Lalala I love you El'

`UNICODE_CHAR()`

Character from Unicode code point

Result type

CHAR(1) CHARACTER SET UTF8

Syntax

UNICODE_CHAR (code)

Table 1. `UNICODE_CHAR` Function Parameter
Parameter	Description
code	The Unicode code point (range 0…0x10FFFF)

Returns the character corresponding to the Unicode code point passed in the argument.

`UNICODE_VAL()`

Unicode code point from string

Result type

INTEGER

Syntax

UNICODE_VAL (ch)

Table 1. `UNICODE_VAL` Function Parameter
Parameter	Description
ch	A string of the `[VAR]CHAR` data type or a text `BLOB`

Returns the Unicode code point (range 0…0x10FFFF) of the character passed in.

If the argument is a string with more than one character, the Unicode code point of the first character is returned.
If the argument is an empty string, 0 is returned.
If the argument is NULL, NULL is returned.

`UPPER()`

Converts a string to uppercase

Result type

(VAR)CHAR, (VAR)BINARY or BLOB

Syntax

UPPER (str)

Table 1. `UPPER` Function Parameter
Parameter	Description
str	An expression of a string type

Returns the uppercase equivalent of the input string.The exact result depends on the character set.With ASCII or NONE for instance, only ASCII characters are uppercased;with character set OCTETS/(VAR)BINARY, the entire string is returned unchanged.

`UPPER` Examples

select upper(_iso8859_1 'Débâcle')
from rdb$database
-- returns 'DÉBÂCLE'

select upper(_iso8859_1 'Débâcle' collate fr_fr)
from rdb$database
-- returns 'DEBACLE', following French uppercasing rules

See also

[fblangref50-scalarfuncs-lower]

`BASE64_DECODE()`

Decodes a base64 string to binary

Result type

VARBINARY or BLOB

Syntax

BASE64_DECODE (base64_data)

Table 1. `BASE64_DECODE` Function Parameter
Parameter	Description
base64_data	Base64 encoded data, padded with `=` to multiples of 4

BASE64_DECODE decodes a string with base64-encoded data, and returns the decoded value as VARBINARY or BLOB as appropriate for the input.If the length of the type of base64_data is not a multiple of 4, an error is raised at prepare time.If the length of the value of base64_data is not a multiple of 4, an error is raised at execution time.

When the input is not BLOB, the length of the resulting type is calculated as type_length * 3 / 4, where type_length is the maximum length in characters of the input type.

Example of `BASE64_DECODE`

select cast(base64_decode('VGVzdCBiYXNlNjQ=') as varchar(12))
from rdb$database;

CAST
============
Test base64

`BASE64_ENCODE()`

Encodes a (binary) value to a base64 string

Result type

VARCHAR CHARACTER SET ASCII or BLOB SUB_TYPE TEXT CHARACTER SET ASCII

Syntax

BASE64_ENCODE (binary_data)

Table 1. `BASE64_ENCODE` Function Parameter
Parameter	Description
binary_data	Binary data (or otherwise convertible to binary) to encode

BASE64_ENCODE encodes binary_data with base64, and returns the encoded value as a VARCHAR CHARACTER SET ASCII or BLOB SUB_TYPE TEXT CHARACTER SET ASCII as appropriate for the input.The returned value is padded with ‘=’ so its length is a multiple of 4.

When the input is not BLOB, the length of the resulting type is calculated as type_length * 4 / 3 rounded up to a multiple of four, where type_length is the maximum length in bytes of the input type.If this length exceeds the maximum length of VARCHAR, the function returns a BLOB.

Example of `BASE64_ENCODE`

select base64_encode('Test base64')
from rdb$database;

BASE64_ENCODE
================
VGVzdCBiYXNlNjQ=

`BIT_LENGTH()`

String or binary length in bits

Result type

INTEGER, or BIGINT for BLOB

Syntax

BIT_LENGTH (string)

Table 1. `BIT_LENGTH` Function Parameter
Parameter	Description
string	An expression of a string type

Gives the length in bits of the input string.For multi-byte character sets, this may be less than the number of characters times 8 times the “formal” number of bytes per character as found in RDB$CHARACTER_SETS.

Note	With arguments of type `CHAR`, this function takes the entire formal string length (i.e. the declared length of a field or variable) into account.If you want to obtain the “logical” bit length, not counting the trailing spaces, right-`TRIM` the argument before passing it to `BIT_LENGTH`.

`BIT_LENGTH` Examples

select bit_length('Hello!') from rdb$database
-- returns 48

select bit_length(_iso8859_1 'Grüß di!') from rdb$database
-- returns 64: ü and ß take up one byte each in ISO8859_1

select bit_length
  (cast (_iso8859_1 'Grüß di!' as varchar(24) character set utf8))
from rdb$database
-- returns 80: ü and ß take up two bytes each in UTF8

select bit_length
  (cast (_iso8859_1 'Grüß di!' as char(24) character set utf8))
from rdb$database
-- returns 208: all 24 CHAR positions count, and two of them are 16-bit

`BLOB_APPEND()`

Efficient concatenation of blobs

Result type

BLOB

Syntax

BLOB_APPEND(expr1, expr2 [, exprN ... ])

Table 1. `BLOB_APPEND` Function Parameters
Parameter	Description
exprN	An expression of a type convertible to `BLOB`

The BLOB_APPEND function concatenates blobs without creating intermediate BLOBs, avoiding excessive memory consumption and growth of the database file.The BLOB_APPEND function takes two or more arguments and adds them to a BLOB which remains open for further modification by a subsequent BLOB_APPEND call.

The resulting BLOB is left open for writing instead of being closed when the function returns.In other words, the BLOB can be appended as many times as required.The engine marks the BLOB returned by BLOB_APPEND with an internal flag, BLB_close_on_read, and closes it automatically when needed.

The first argument determines the behaviour of the function:

NULL: new, empty BLOB SUB_TYPE TEXT is created, using the connection character set as the character set
permanent BLOB (from a table) or temporary BLOB which was already closed: new BLOB is created with the same subtype and, if subtype is TEXT the same character set, populated with the content of the original BLOB.
temporary unclosed BLOB with the BLB_close_on_read flag (e.g. created by another call to BLOB_APPEND): used as-is, remaining arguments are appended to this BLOB
other data types: a new BLOB SUB_TYPE TEXT is created, populated with the original argument converted to string.If the original value is a character type, its character set is used (for string literals, the connection character set), otherwise the connection character set.

Other arguments can be of any type.The following behavior is defined for them:

NULLs are ignored (behaves as empty string)
BLOBs, if necessary, are transliterated to the character set of the first argument and their contents are appended to the result
other data types are converted to strings (as usual) and appended to the result

The BLOB_APPEND function returns a temporary unclosed BLOB with the BLB_close_on_read flag.If the first argument is such a temporary unclosed BLOB (e.g. created by a previous call to BLOB_APPEND), it will be used as-is, otherwise a new BLOB is created.Thus, a series of operations like blob = BLOB_APPEND (blob, …) will result in the creation of at most one BLOB (unless you try to append a BLOB to itself).This blob will be automatically closed by the engine when the client reads it, assigns it to a table, or uses it in other expressions that require reading the content.

Warning

Important caveats for BLOB_APPEND

The NULL behaviour of BLOB_APPEND is different from normal concatenation (using ||).Occurrence of NULL will behave as if an empty string was used.In other words, NULL is effectively ignored.

In normal concatenation, concatenating with NULL results in NULL.

Note	Testing a blob for `NULL` using the `IS [NOT] NULL` operator does not read it and therefore a temporary blob with the `BLB_close_on_read` flag will not be closed after such a test.

Tip	Use `LIST` or `BLOB_APPEND` functions to concatenate blobs.This reduces memory consumption and disk I/O, and also prevents database growth due to the creation of many temporary blobs when using the concatenation operator.

`BLOB_APPEND` Examples

execute block
returns (b blob sub_type text)
as
begin
  -- creates a new temporary not closed BLOB
  -- and writes the string from the 2nd argument into it
  b = blob_append(null, 'Hello ');

  -- adds two strings to the temporary BLOB without closing it
  b = blob_append(b, 'World', '!');

  -- comparing a BLOB with a string will close it, because the BLOB needs to be read
  if (b = 'Hello World!') then
  begin
  -- ...
  end

  -- creates a temporary closed BLOB by adding a string to it
  b = b || 'Close';

  suspend;
end

`CHAR_LENGTH()`, `CHARACTER_LENGTH()`

String length in characters

Result type

INTEGER, or BIGINT for BLOB

Syntax

  CHAR_LENGTH (string)
| CHARACTER_LENGTH (string)

Table 1. `CHAR[ACTER]_LENGTH` Function Parameter
Parameter	Description
string	An expression of a string type

Gives the length in characters of the input string.

Note

With arguments of type CHAR, this function returns the formal string length (i.e. the declared length of a field or variable).If you want to obtain the “logical” length, not counting the trailing spaces, right-TRIM the argument before passing it to CHAR[ACTER]_LENGTH.
This function fully supports text BLOBs of any length and character set.

`CHAR_LENGTH` Examples

select char_length('Hello!') from rdb$database
-- returns 6

select char_length(_iso8859_1 'Grüß di!') from rdb$database
-- returns 8

select char_length
  (cast (_iso8859_1 'Grüß di!' as varchar(24) character set utf8))
from rdb$database
-- returns 8; the fact that ü and ß take up two bytes each is irrelevant

select char_length
  (cast (_iso8859_1 'Grüß di!' as char(24) character set utf8))
from rdb$database
-- returns 24: all 24 CHAR positions count

`CRYPT_HASH()`

Cryptographic hash

Result type

VARBINARY

Syntax

CRYPT_HASH (value USING <hash>)

<hash> ::= MD5 | SHA1 | SHA256 | SHA512

Table 1. `CRYPT_HASH` Function Parameter
Parameter	Description
value	Expression of value of any type;non-string or non-binary types are converted to string
hash	Cryptographic hash algorithm to apply

CRYPT_HASH returns a cryptographic hash calculated from the input argument using the specified algorithm.If the input argument is not a string or binary type, it is converted to string before hashing.

This function returns a VARBINARY with the length depending on the specified algorithm.

Note

The MD5 and SHA1 algorithms are not recommended for security purposes due to known attacks to generate hash collisions.These two algorithms are provided for backward-compatibility only.
When hashing string or binary values, take into account the effects of trailing blanks (spaces or NULs).The value 'ab' in a CHAR(5) (3 trailing spaces) has a different hash than if it is stored in a VARCHAR(5) (no trailing spaces) or CHAR(6) (4 trailing spaces).

To avoid this, make sure you always use a variable length data type, or the same fixed length data type, or normalize values before hashing, for example using TRIM(TRAILING FROM value).

Examples of `CRYPT_HASH`

Hashing x with the SHA512 algorithm

select crypt_hash(x using sha512) from y;

See also

[fblangref50-scalarfuncs-hash]

`HASH()`

Non-cryptographic hash

Result type

INTEGER, BIGINT

Syntax

HASH (value [USING <hash>])

<hash> ::= CRC32

Table 1. `HASH` Function Parameter
Parameter	Description
value	Expression of value of any type;non-string or non-binary types are converted to string
hash	Non-cryptographic hash algorithm to apply

HASH returns a hash value for the input argument.If the input argument is not a string or binary type, it is converted to string before hashing.

The optional USING clause specifies the non-cryptographic hash algorithm to apply.When the USING clause is absent, the legacy PJW algorithm is applied;this is identical to its behaviour in previous Firebird versions.

This function fully supports text BLOBs of any length and character set.

Supported algorithms

not specified: When no algorithm is specified, Firebird applies the 64-bit variant of the non-cryptographic PJW hash function (also known as ELF64).This is a fast algorithm for general purposes (hash tables, etc.), but its collision quality is suboptimal.Other hash functions — specified explicitly in the USING clause, or cryptographic hashes through [fblangref50-scalarfuncs-crypthash] — should be used for more reliable hashing.

The HASH function returns BIGINT for this algorithm
CRC32: With CRC32, Firebird applies the CRC32 algorithm using the polynomial 0x04C11DB7.

The HASH function returns INTEGER for this algorithm.

Examples of `HASH`

Hashing x with the CRC32 algorithm
```
select hash(x using crc32) from y;
```
Hashing x with the legacy PJW algorithm
```
select hash(x) from y;
```

See also

[fblangref50-scalarfuncs-crypthash]

Date and Time Functions

`DATEADD()`

Adds or subtracts datetime units from a datetime value

Result type

DATE, TIME or TIMESTAMP

Syntax

DATEADD (<args>)

<args> ::=
    <amount> <unit> TO <datetime>
  | <unit>, <amount>, <datetime>

<amount> ::= an integer expression (negative to subtract)
<unit> ::=
    YEAR | MONTH | WEEK | DAY
  | HOUR | MINUTE | SECOND | MILLISECOND
<datetime> ::= a DATE, TIME or TIMESTAMP expression

Table 1. `DATEADD` Function Parameters
Parameter	Description
amount	An integer expression of the `SMALLINT`, `INTEGER` or `BIGINT` type.For unit `MILLISECOND`, the type is `NUMERIC(18, 1)`.A negative value is subtracted.
unit	Date/time unit
datetime	An expression of the `DATE`, `TIME` or `TIMESTAMP` type

Adds the specified number of years, months, weeks, days, hours, minutes, seconds or milliseconds to a date/time value.

The result type is determined by the third argument.
With TIMESTAMP and DATE arguments, all units can be used.
With TIME arguments, only HOUR, MINUTE, SECOND and MILLISECOND can be used.

Examples of `DATEADD`

dateadd (28 day to current_date)
dateadd (-6 hour to current_time)
dateadd (month, 9, DateOfConception)
dateadd (-38 week to DateOfBirth)
dateadd (minute, 90, cast('now' as time))
dateadd (? year to date '11-Sep-1973')

select
  cast(dateadd(-1 * extract(millisecond from ts) millisecond to ts) as varchar(30)) as t,
  extract(millisecond from ts) as ms
from (
  select timestamp '2014-06-09 13:50:17.4971' as ts
  from rdb$database
) a

T                        MS
------------------------ ------
2014-06-09 13:50:17.0000  497.1

`DATEDIFF()`

Difference between two datetime values in a datetime unit

Result type

BIGINT, or NUMERIC(18,1) for MILLISECOND

Syntax

DATEDIFF (<args>)

<args> ::=
    <unit> FROM <moment1> TO <moment2>
  | <unit>, <moment1>, <moment2>

<unit> ::=
    YEAR | MONTH | WEEK | DAY
  | HOUR | MINUTE | SECOND | MILLISECOND
<momentN> ::= a DATE, TIME or TIMESTAMP expression

Table 1. `DATEDIFF` Function Parameters
Parameter	Description
unit	Date/time unit
moment1	An expression of the `DATE`, `TIME` or `TIMESTAMP` type
moment2	An expression of the `DATE`, `TIME` or `TIMESTAMP` type

Returns the number of years, months, weeks, days, hours, minutes, seconds or milliseconds elapsed between two date/time values.

DATE and TIMESTAMP arguments can be combined.No other mixes are allowed.
With TIMESTAMP and DATE arguments, all units can be used.
With TIME arguments, only HOUR, MINUTE, SECOND and MILLISECOND can be used.

Computation

DATEDIFF doesn’t look at any smaller units than the one specified in the first argument.As a result,
- datediff (year, date '1-Jan-2009', date '31-Dec-2009') returns 0, but
- datediff (year, date '31-Dec-2009', date '1-Jan-2010') returns 1
It does, however, look at all the bigger units. So:
- datediff (day, date '26-Jun-1908', date '11-Sep-1973') returns 23818
A negative result value indicates that moment2 lies before moment1.

`DATEDIFF` Examples

datediff (hour from current_timestamp to timestamp '12-Jun-2059 06:00')
datediff (minute from time '0:00' to current_time)
datediff (month, current_date, date '1-1-1900')
datediff (day from current_date to cast(? as date))

`EXTRACT()`

Extracts a datetime unit from a datetime value

Result type

SMALLINT or NUMERIC

Syntax

EXTRACT (<part> FROM <datetime>)

<part> ::=
    YEAR | MONTH | QUARTER | WEEK
  | DAY | WEEKDAY | YEARDAY
  | HOUR | MINUTE | SECOND | MILLISECOND
  | TIMEZONE_HOUR | TIMEZONE_MINUTE
<datetime> ::= a DATE, TIME or TIMESTAMP expression

Table 1. `EXTRACT` Function Parameters
Parameter	Description
part	Date/time unit
datetime	An expression of the `DATE`, `TIME` or `TIMESTAMP` type

Extracts and returns an element from a DATE, TIME or TIMESTAMP expression.

Returned Data Types and Ranges

The returned data types and possible ranges are shown in the table below.If you try to extract a part that isn’t present in the date/time argument (e.g. SECOND from a DATE or YEAR from a TIME), an error occurs.

Table 1. Types and ranges of `EXTRACT` results
Part	Type	Range	Comment
`YEAR`	`SMALLINT`	1-9999
`MONTH`	`SMALLINT`	1-12
`QUARTER`	`SMALLINT`	1-4
`WEEK`	`SMALLINT`	1-53
`DAY`	`SMALLINT`	1-31
`WEEKDAY`	`SMALLINT`	0-6	0 = Sunday
`YEARDAY`	`SMALLINT`	0-365	0 = January 1
`HOUR`	`SMALLINT`	0-23
`MINUTE`	`SMALLINT`	0-59
`SECOND`	`NUMERIC(9,4)`	0.0000-59.9999	includes millisecond as fraction
`MILLISECOND`	`NUMERIC(9,1)`	0.0-999.9
`TIMEZONE_HOUR`	`SMALLINT`	-23 - +23
`TIMEZONE_MINUTE`	`SMALLINT`	-59 - +59

`MILLISECOND`

Extracts the millisecond value from a TIME or TIMESTAMP.The data type returned is NUMERIC(9,1).

Note	If you extract the millisecond from [fblangref50-contextvars-current-time], be aware that this variable defaults to seconds precision, so the result will always be 0.Extract from `CURRENT_TIME(3)` or [fblangref50-contextvars-current-timestamp] to get milliseconds precision.

`WEEK`

Extracts the ISO-8601 week number from a DATE or TIMESTAMP.ISO-8601 weeks start on a Monday and always have the full seven days.Week 1 is the first week that has a majority (at least 4) of its days in the new year.The first 1-3 days of the year may belong to the last week (52 or 53) of the previous year.Likewise, a year’s final 1-3 days may belong to week 1 of the following year.

Caution

Be careful when combining WEEK and YEAR results.For instance, 30 December 2008 lies in week 1 of 2009, so extract(week from date '30 Dec 2008') returns 1.However, extracting YEAR always gives the calendar year, which is 2008.In this case, WEEK and YEAR are at odds with each other.The same happens when the first days of January belong to the last week of the previous year.

Please also notice that WEEKDAY is not ISO-8601 compliant: it returns 0 for Sunday, whereas ISO-8601 specifies 7.

See also

Data Types for Dates and Times

`FIRST_DAY()`

Returns the first day of a time period containing a datetime value

Result Type

DATE, TIMESTAMP (with or without time zone)

Syntax

FIRST_DAY(OF <period> FROM date_or_timestamp)

<period> ::= YEAR | MONTH | QUARTER | WEEK

Table 1. `FIRST_DAY` Function Parameters
Parameter	Description
date_or_timestamp	Expression of type `DATE`, `TIMESTAMP WITHOUT TIME ZONE` or `TIMESTAMP WITH TIME ZONE`

FIRST_DAY returns a date or timestamp (same as the type of date_or_timestamp) with the first day of the year, month or week of a given date or timestamp value.

Note	The first day of the week is considered as Sunday, following the same rules as for [fblangref50-scalarfuncs-extract] with `WEEKDAY`. When a timestamp is passed, the return value preserves the time part.

Examples of `FIRST_DAY`

select
  first_day(of month from current_date),
  first_day(of year from current_timestamp),
  first_day(of week from date '2017-11-01'),
  first_day(of quarter from date '2017-11-01')
from rdb$database;

`LAST_DAY()`

Returns the last day of a time period containing a datetime value

Result Type

DATE, TIMESTAMP (with or without time zone)

Syntax

LAST_DAY(OF <period> FROM date_or_timestamp)

<period> ::= YEAR | MONTH | QUARTER | WEEK

Table 1. `LAST_DAY` Function Parameters
Parameter	Description
date_or_timestamp	Expression of type `DATE`, `TIMESTAMP WITHOUT TIME ZONE` or `TIMESTAMP WITH TIME ZONE`

LAST_DAY returns a date or timestamp (same as the type of date_or_timestamp) with the last day of the year, month or week of a given date or timestamp value.

Note	The last day of the week is considered as Saturday, following the same rules as for [fblangref50-scalarfuncs-extract] with `WEEKDAY`. When a timestamp is passed, the return value preserves the time part.

Examples of `LAST_DAY`

select
  last_day(of month from current_date),
  last_day(of year from current_timestamp),
  last_day(of week from date '2017-11-01'),
  last_day(of quarter from date '2017-11-01')
from rdb$database;

Type Casting Functions

`CAST()`

Converts a value from one data type to another

Result type

As specified by target_type

Syntax

CAST (<expression> AS <target_type>)

<target_type> ::= <domain_or_non_array_type> | <array_datatype>

<domain_or_non_array_type> ::=
  !! See Scalar Data Types Syntax !!

<array_datatype> ::=
  !! See Array Data Types Syntax !!

Table 1. `CAST` Function Parameters
Parameter	Description
expression	SQL expression
sql_datatype	SQL data type

CAST converts an expression to the desired data type or domain.If the conversion is not possible, an error is raised.

“Shorthand” Syntax

Alternative syntax, supported only when casting a string literal to a DATE, TIME or TIMESTAMP:

datatype 'date/timestring'

This syntax was already available in InterBase, but was never properly documented.In the SQL standard, this feature is called “datetime literals”.

Note	Since Firebird 4.0, the use of `'NOW'`, `'YESTERDAY'` and `'TOMORROW'` in the shorthand cast is no longer allowed;only literals defining a fixed moment in time are supported.

Allowed Type Conversions

The following table shows the type conversions possible with CAST.

Table 1. Possible Type-castings with `CAST`
From	To
Numeric types	Numeric types `[VAR]CHAR` `BLOB`
`[VAR]CHAR` `BLOB`	`[VAR]CHAR` `BLOB` Numeric types `DATE` `TIME` `TIMESTAMP`
`DATE` `TIME`	`[VAR]CHAR` `BLOB` `TIMESTAMP`
`TIMESTAMP`	`[VAR]CHAR` `BLOB` `DATE` `TIME`

Keep in mind that sometimes information is lost, for instance when you cast a TIMESTAMP to a DATE.Also, the fact that types are CAST-compatible is in itself no guarantee that a conversion will succeed.“CAST(123456789 as SMALLINT)” will definitely result in an error, as will “CAST('Judgement Day' as DATE)”.

Casting Parameters

You can also cast statement parameters to a data type:

cast (? as integer)

This gives you control over the type of the parameter set up by the engine.Please notice that with statement parameters, you always need a full-syntax cast — shorthand casts are not supported.

Casting to a Domain or its Type

Casting to a domain or its base type are supported.When casting to a domain, any constraints (NOT NULL and/or CHECK) declared for the domain must be satisfied, or the cast will fail.Please be aware that a CHECK passes if it evaluates to TRUE or NULL!So, given the following statements:

create domain quint as int check (value >= 5000);
select cast (2000 as quint) from rdb$database;     -- (1)
select cast (8000 as quint) from rdb$database;     -- (2)
select cast (null as quint) from rdb$database;     -- (3)

only cast number 1 will result in an error.

When the TYPE OF modifier is used, the expression is cast to the base type of the domain, ignoring any constraints.With domain quint defined as above, the following two casts are equivalent and will both succeed:

select cast (2000 as type of quint) from rdb$database;
select cast (2000 as int) from rdb$database;

If TYPE OF is used with a (VAR)CHAR type, its character set and collation are retained:

create domain iso20 varchar(20) character set iso8859_1;
create domain dunl20 varchar(20) character set iso8859_1 collate du_nl;
create table zinnen (zin varchar(20));
commit;
insert into zinnen values ('Deze');
insert into zinnen values ('Die');
insert into zinnen values ('die');
insert into zinnen values ('deze');

select cast(zin as type of iso20) from zinnen order by 1;
-- returns Deze -> Die -> deze -> die

select cast(zin as type of dunl20) from zinnen order by 1;
-- returns deze -> Deze -> die -> Die

Warning

If a domain’s definition is changed, existing CASTs to that domain or its type may become invalid.If these CASTs occur in PSQL modules, their invalidation may be detected.See the note The RDB$VALID_BLR field, in Appendix A.

Casting to a Column’s Type

It is also possible to cast expressions to the type of an existing table or view column.Only the type itself is used;in the case of string types, this includes the character set but not the collation.Constraints and default values of the source column are not applied.

create table ttt (
  s varchar(40) character set utf8 collate unicode_ci_ai
);
commit;

select cast ('Jag har många vänner' as type of column ttt.s)
from rdb$database;

Warning

Warnings

If a column’s definition is altered, existing CASTs to that column’s type may become invalid.If these CASTs occur in PSQL modules, their invalidation may be detected.See the note The RDB$VALID_BLR field, in Appendix A.

Cast Examples

A full-syntax cast:

select cast ('12' || '-June-' || '1959' as date) from rdb$database

A shorthand string-to-date cast:

update People set AgeCat = 'Old'
  where BirthDate < date '1-Jan-1943'

Notice that you can drop even the shorthand cast from the example above, as the engine will understand from the context (comparison to a DATE field) how to interpret the string:

update People set AgeCat = 'Old'
  where BirthDate < '1-Jan-1943'

However, this is not always possible.The cast below cannot be dropped, otherwise the engine would find itself with an integer to be subtracted from a string:

select cast('today' as date) - 7 from rdb$database

Bitwise Functions

`BIN_AND()`

Bitwise AND

Result type

integer type (the widest type of the arguments)

Note	`SMALLINT` result is returned only if all the arguments are explicit `SMALLINT`s or `NUMERIC(n, 0)` with n <= 4;otherwise small integers return an `INTEGER` result.

Syntax

BIN_AND (number, number [, number ...])

Table 1. `BIN_AND` Function Parameters
Parameter	Description
number	A number of an integer type

Returns the result of the bitwise AND operation on the argument(s).

`BIN_NOT()`

Bitwise NOT

Result type

integer type matching the argument

Note	`SMALLINT` result is returned only if all the arguments are explicit `SMALLINT`s or `NUMERIC(n, 0)` with n <= 4;otherwise small integers return an `INTEGER` result.

Syntax

BIN_NOT (number)

Table 1. `BIN_NOT` Function Parameter
Parameter	Description
number	A number of an integer type

Returns the result of the bitwise NOT operation on the argument, i.e. one’s complement.

`BIN_OR()`

Bitwise OR

Result type

integer type (the widest type of the arguments)

Note	`SMALLINT` result is returned only if all the arguments are explicit `SMALLINT`s or `NUMERIC(n, 0)` with n <= 4;otherwise small integers return an `INTEGER` result.

Syntax

BIN_OR (number, number [, number ...])

Table 1. `BIN_OR` Function Parameters
Parameter	Description
number	A number of an integer type

Returns the result of the bitwise OR operation on the argument(s).

`BIN_SHL()`

Bitwise left-shift

Result type

BIGINT or INT128 depending on the first argument

Syntax

BIN_SHL (number, shift)

Table 1. `BIN_SHL` Function Parameters
Parameter	Description
number	A number of an integer type
shift	The number of bits the number value is shifted by

Returns the first argument bitwise left-shifted by the second argument, i.e. a << b or a·2^b.

See also

[fblangref50-scalarfuncs-bin-shr]

`BIN_SHR()`

Bitwise right-shift with sign extension

Result type

BIGINT or INT128 depending on the first argument

Syntax

BIN_SHR (number, shift)

Table 1. `BIN_SHR` Function Parameters
Parameter	Description
number	A number of an integer type
shift	The number of bits the number value is shifted by

Returns the first argument bitwise right-shifted by the second argument, i.e. a >> b or a/2^b.

The operation performed is an arithmetic right shift (x86 SAR), meaning that the sign of the first operand is always preserved.

See also

[fblangref50-scalarfuncs-bin-shl]

`BIN_XOR()`

Bitwise XOR

Result type

integer type (the widest type of the arguments)

Note	`SMALLINT` result is returned only if all the arguments are explicit `SMALLINT`s or `NUMERIC(n, 0)` with n <= 4;otherwise small integers return an `INTEGER` result.

Syntax

BIN_XOR (number, number [, number ...])

Table 1. `BIN_XOR` Function Parameters
Parameter	Description
number	A number of an integer type

Returns the result of the bitwise XOR operation on the argument(s).

UUID Functions

`CHAR_TO_UUID()`

Converts a string UUID to its binary representation

Result type

BINARY(16)

Syntax

CHAR_TO_UUID (ascii_uuid)

Table 1. `CHAR_TO_UUID` Function Parameter
Parameter	Description
ascii_uuid	A 36-character representation of UUID.‘`-`’ (hyphen) in positions 9, 14, 19 and 24;valid hexadecimal digits in any other positions, e.g. 'A0bF4E45-3029-2a44-D493-4998c9b439A3'

Converts a human-readable 36-char UUID string to the corresponding 16-byte UUID.

`CHAR_TO_UUID` Examples

select char_to_uuid('A0bF4E45-3029-2a44-D493-4998c9b439A3') from rdb$database
-- returns A0BF4E4530292A44D4934998C9B439A3 (16-byte string)

select char_to_uuid('A0bF4E45-3029-2A44-X493-4998c9b439A3') from rdb$database
-- error: -Human readable UUID argument for CHAR_TO_UUID must
--         have hex digit at position 20 instead of "X (ASCII 88)"

`GEN_UUID()`

Generates a random binary UUID

Result type

BINARY(16)

Syntax

GEN_UUID ()

Returns a universally unique ID as a 16-byte character string.

`GEN_UUID` Example

select gen_uuid() from rdb$database
-- returns e.g. 017347BFE212B2479C00FA4323B36320 (16-byte string)

`UUID_TO_CHAR()`

Converts a binary UUID to its string representation

Result type

CHAR(36)

Syntax

UUID_TO_CHAR (uuid)

Table 1. `UUID_TO_CHAR` Function Parameters
Parameter	Description
uuid	16-byte UUID

Converts a 16-byte UUID to its 36-character, human-readable ASCII representation.

`UUID_TO_CHAR` Examples

select uuid_to_char(x'876C45F4569B320DBCB4735AC3509E5F') from rdb$database
-- returns '876C45F4-569B-320D-BCB4-735AC3509E5F'

select uuid_to_char(gen_uuid()) from rdb$database
-- returns e.g. '680D946B-45FF-DB4E-B103-BB5711529B86'

select uuid_to_char('Firebird swings!') from rdb$database
-- returns '46697265-6269-7264-2073-77696E677321'

Functions for Sequences (Generators)

`GEN_ID()`

Increments a sequence (generator) value and returns its new value

Result type

BIGINT — dialect 2 and 3
INTEGER — dialect 1

Syntax

GEN_ID (generator-name, step)

Table 1. `GEN_ID` Function Parameters
Parameter	Description
generator-name	Identifier name of a generator (sequence)
step	An integer expression of the increment

If step equals 0, the function will leave the value of the generator unchanged and return its current value.

The SQL-compliant NEXT VALUE FOR syntax is preferred, except when an increment other than the configured increment of the sequence is needed.

Warning

If the value of the step parameter is less than zero, it will decrease the value of the generator.You should be cautious with such manipulations in the database, as they could compromise data integrity (meaning, subsequent insert statements could fail due to generating of duplicate id values).

Note	In dialect 1, the result type is `INTEGER`, in dialect 2 and 3 it is `BIGINT`.

`GEN_ID` Example

new.rec_id = gen_id(gen_recnum, 1);

Conditional Functions

`COALESCE()`

Returns the first non-NULL argument

Result type

Depends on input

Syntax

COALESCE (<exp1>, <exp2> [, <expN> ... ])

Table 1. `COALESCE` Function Parameters
Parameter	Description
exp1, exp2 … expN	A list of expressions of compatible types

The COALESCE function takes two or more arguments and returns the value of the first non-NULL argument.If all the arguments evaluate to NULL, the result is NULL.

`COALESCE` Examples

This example picks the Nickname from the Persons table.If it happens to be NULL, it goes on to FirstName.If that too is NULL, “'Mr./Mrs.'” is used.Finally, it adds the family name.All in all, it tries to use the available data to compose a full name that is as informal as possible.This scheme only works if absent nicknames and first names are NULL: if one of them is an empty string, COALESCE will happily return that to the caller.That problem can be fixed by using [fblangref50-scalarfuncs-nullif].

select
  coalesce (Nickname, FirstName, 'Mr./Mrs.') || ' ' || LastName
    as FullName
from Persons

`DECODE()`

Shorthand “simple CASE”-equivalent function

Result type

Depends on input

Syntax

DECODE(<testexpr>,
  <expr1>, <result1>
  [<expr2>, <result2> ...]
  [, <defaultresult>])

Table 1. `DECODE` Function Parameters
Parameter	Description
testexpr	An expression of any compatible type that is compared to the expressions expr1, expr2 … exprN
expr1, expr2, … exprN	Expressions of any compatible types, to which the testexpr expression is compared
result1, result2, … resultN	Returned values of any type
defaultresult	The expression to be returned if none of the conditions is met

DECODE is a shorthand for the so-called “simple CASE” construct, in which a given expression is compared to a number of other expressions until a match is found.The result is determined by the value listed after the matching expression.If no match is found, the default result is returned, if present, otherwise NULL is returned.

The equivalent CASE construct:

CASE <testexpr>
  WHEN <expr1> THEN <result1>
  [WHEN <expr2> THEN <result2> ...]
  [ELSE <defaultresult>]
END

Caution

Matching is done with the ‘=’ operator, so if testexpr is NULL, it won’t match any of the exprs, not even those that are NULL.

`DECODE` Examples

select name,
  age,
  decode(upper(sex),
         'M', 'Male',
         'F', 'Female',
         'Unknown'),
  religion
from people

See also

CASE, Simple CASE

`IIF()`

Ternary conditional function

Result type

Depends on input

Syntax

IIF (<condition>, ResultT, ResultF)

Table 1. `IIF` Function Parameters
Parameter	Description
condition	A true\|false expression
resultT	The value returned if the condition is true
resultF	The value returned if the condition is false

IIF takes three arguments.If the first evaluates to true, the second argument is returned;otherwise the third is returned.

IIF could be likened to the ternary “<condition> ? resultT : resultF” operator in C-like languages.

Note	`IIF(<condition>, resultT, resultF)` is a shorthand for “`CASE WHEN <condition> THEN resultT ELSE resultF END`”.

`IIF` Examples

select iif( sex = 'M', 'Sir', 'Madam' ) from Customers

`MAXVALUE()`

Returns the maximum value of its arguments

Result type

Varies according to input — result will be of the same data type as the first expression in the list (expr1).

Syntax

MAXVALUE (<expr1> [, ... , <exprN> ])

Table 1. `MAXVALUE` Function Parameters
Parameter	Description
expr1 … exprN	List of expressions of compatible types

Returns the maximum value from a list of numerical, string, or date/time expressions.This function fully supports text BLOBs of any length and character set.

If one or more expressions resolve to NULL, MAXVALUE returns NULL.This behaviour differs from the aggregate function MAX.

`MAXVALUE` Examples

SELECT MAXVALUE(PRICE_1, PRICE_2) AS PRICE
  FROM PRICELIST

See also

[fblangref50-scalarfuncs-minvalue]

`MINVALUE()`

Returns the minimum value of its arguments

Result type

Varies according to input — result will be of the same data type as the first expression in the list (expr1).

Syntax

MINVALUE (<expr1> [, ... , <exprN> ])

Table 1. `MINVALUE` Function Parameters
Parameter	Description
expr1 … exprN	List of expressions of compatible types

Returns the minimum value from a list of numerical, string, or date/time expressions.This function fully supports text BLOBs of any length and character set.

If one or more expressions resolve to NULL, MINVALUE returns NULL.This behaviour differs from the aggregate function MIN.

`MINVALUE` Examples

SELECT MINVALUE(PRICE_1, PRICE_2) AS PRICE
  FROM PRICELIST

See also

[fblangref50-scalarfuncs-maxvalue]

`NULLIF()`

Conditional NULL function

Result type

Depends on input

Syntax

NULLIF (<exp1>, <exp2>)

Table 1. `NULLIF` Function Parameters
Parameter	Description
exp1	An expression
exp2	Another expression of a data type compatible with exp1

NULLIF returns the value of the first argument, unless it is equal to the second.In that case, NULL is returned.

`NULLIF` Example

select avg( nullif(Weight, -1) ) from FatPeople

This will return the average weight of the persons listed in FatPeople, excluding those having a weight of -1, since AVG skips NULL data.Presumably, -1 indicates “weight unknown” in this table.A plain AVG(Weight) would include the -1 weights, thus skewing the result.

RDB$GET_CONTEXT()

RDB$GET_CONTEXT()

The SYSTEM Namespace

docnext count = 168

The DDL_TRIGGER Namespace

Examples

RDB$SET_CONTEXT()

Special Functions for DECFLOAT

COMPARE_DECFLOAT()

NORMALIZE_DECFLOAT()

Examples of NORMALIZE_DECFLOAT

QUANTIZE()

Examples of QUANTIZE

TOTALORDER()

Cryptographic Functions

DECRYPT()

DECRYPT Examples

ENCRYPT()

ENCRYPT Examples

RSA_DECRYPT()

RSA_DECRYPT Examples

RSA_ENCRYPT()

RSA_ENCRYPT Examples

RSA_PRIVATE()

RSA_PRIVATE Examples

RSA_PUBLIC()

RSA_PUBLIC Examples

RSA_SIGN_HASH()

RSA_SIGN_HASH Examples

RSA_VERIFY_HASH()

RSA_VERIFY_HASH Examples

Other Functions

MAKE_DBKEY()

Examples of MAKE_DBKEY

RDB$ERROR()

Example of RDB$ERROR

RDB$GET_TRANSACTION_CN()

RDB$GET_TRANSACTION_CN Examples

RDB$ROLE_IN_USE()

RDB$ROLE_IN_USE Examples

RDB$SYSTEM_PRIVILEGE()

RDB$SYSTEM_PRIVILEGE Examples

Mathematical Functions

ABS()

COS()

COSH()

COT()

EXP()

FLOOR()

LN()

LOG()

LOG10()

MOD()

PI()

ACOS()

POWER()

RAND()

ROUND()

ROUND Examples

SIGN()

SIN()

SINH()

SQRT()

TAN()

TANH()

TRUNC()

ACOSH()

ASIN()

ASINH()

ATAN()

ATAN2()

ATANH()

CEIL(), CEILING()

String and Binary Functions

ASCII_CHAR()

HEX_DECODE()

Example of HEX_DECODE

HEX_ENCODE()

Example of HEX_ENCODE

LEFT()

`RDB$GET_CONTEXT()`

The `SYSTEM` Namespace

The `DDL_TRIGGER` Namespace

`RDB$SET_CONTEXT()`

Special Functions for `DECFLOAT`

`COMPARE_DECFLOAT()`

`NORMALIZE_DECFLOAT()`

Examples of `NORMALIZE_DECFLOAT`

`QUANTIZE()`

Examples of `QUANTIZE`

`TOTALORDER()`

`DECRYPT()`

`DECRYPT` Examples

`ENCRYPT()`

`ENCRYPT` Examples

`RSA_DECRYPT()`

`RSA_DECRYPT` Examples

`RSA_ENCRYPT()`

`RSA_ENCRYPT` Examples

`RSA_PRIVATE()`

`RSA_PRIVATE` Examples

`RSA_PUBLIC()`

`RSA_PUBLIC` Examples

`RSA_SIGN_HASH()`

`RSA_SIGN_HASH` Examples

`RSA_VERIFY_HASH()`

`RSA_VERIFY_HASH` Examples

`MAKE_DBKEY()`

Examples of `MAKE_DBKEY`

`RDB$ERROR()`

`RDB$GET_TRANSACTION_CN()`

`RDB$GET_TRANSACTION_CN` Examples

`RDB$ROLE_IN_USE()`

`RDB$ROLE_IN_USE` Examples

`RDB$SYSTEM_PRIVILEGE()`

`RDB$SYSTEM_PRIVILEGE` Examples

`ABS()`

`COS()`

`COSH()`

`COT()`

`EXP()`

`FLOOR()`

`LN()`

`LOG()`

`LOG10()`

`MOD()`

`PI()`

`ACOS()`

`POWER()`

`RAND()`

`ROUND()`

`ROUND` Examples

`SIGN()`

`SIN()`

`SINH()`

`SQRT()`

`TAN()`

`TANH()`

`TRUNC()`

`ACOSH()`

`ASIN()`

`ASINH()`

`ATAN()`

`ATAN2()`

`ATANH()`

`CEIL()`, `CEILING()`

`ASCII_CHAR()`

`HEX_DECODE()`

Example of `HEX_DECODE`

`HEX_ENCODE()`

Example of `HEX_ENCODE`

`LEFT()`

`LOWER()`

`LOWER` Examples

`LPAD()`

`LPAD` Examples

`OCTET_LENGTH()`

`OCTET_LENGTH` Examples

`OVERLAY()`

`OVERLAY` Examples