The Firebird 5.0 Language Reference | Cryptographic Functions | RSA_VERIFY_HASH()

`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;

RSA_VERIFY_HASH Examples

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()

LOWER()

LOWER Examples

LPAD()

LPAD Examples

OCTET_LENGTH()

OCTET_LENGTH Examples

OVERLAY()

OVERLAY Examples

POSITION()

POSITION Examples

REPLACE()

REPLACE Examples

REVERSE()

REVERSE Examples

ASCII_VAL()

RIGHT()

RPAD()

RPAD Examples

SUBSTRING()

Positional SUBSTRING

Regular Expression SUBSTRING

TRIM()

TRIM Examples

UNICODE_CHAR()

UNICODE_VAL()

UPPER()

UPPER Examples

BASE64_DECODE()

Example of BASE64_DECODE

`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

`POSITION()`

`POSITION` Examples

`REPLACE()`

`REPLACE` Examples

`REVERSE()`

`REVERSE` Examples

`ASCII_VAL()`

`RIGHT()`

`RPAD()`

`RPAD` Examples

`SUBSTRING()`

Positional `SUBSTRING`

Regular Expression `SUBSTRING`

`TRIM()`

`TRIM` Examples

`UNICODE_CHAR()`

`UNICODE_VAL()`

`UPPER()`

`UPPER` Examples

`BASE64_DECODE()`

Example of `BASE64_DECODE`

`BASE64_ENCODE()`

Example of `BASE64_ENCODE`

`BIT_LENGTH()`

`BIT_LENGTH` Examples

`BLOB_APPEND()`