FirebirdSQL logo
 Procedural SQL (PSQL) StatementsAggregate Functions 

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'
See also

[fblangref50-scalarfuncs-overlay], [fblangref50-scalarfuncs-substring], [fblangref50-scalarfuncs-position], [fblangref50-scalarfuncs-char-length]

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.

See also

[fblangref50-scalarfuncs-ascii-char], [fblangref50-scalarfuncs-unicode-val]

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.
See also

[fblangref50-scalarfuncs-left], [fblangref50-scalarfuncs-substring]

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>
See also

[fblangref50-scalarfuncs-position], [fblangref50-scalarfuncs-left], [fblangref50-scalarfuncs-right], [fblangref50-scalarfuncs-char-length], SIMILAR TO

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.

See also

[fblangref50-scalarfuncs-unicode-val], [fblangref50-scalarfuncs-ascii-char]

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.

See also

[fblangref50-scalarfuncs-unicode-char], [fblangref50-scalarfuncs-ascii-val]

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
See also

[fblangref50-scalarfuncs-base64encode], [fblangref50-scalarfuncs-hexdecode]

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=
See also

[fblangref50-scalarfuncs-base64decode], [fblangref50-scalarfuncs-hexencode]

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
See also

[fblangref50-scalarfuncs-octet-length], [fblangref50-scalarfuncs-char-length]

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:

  1. NULL: new, empty BLOB SUB_TYPE TEXT is created, using the connection character set as the character set

  2. 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.

  3. 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

  4. 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:

  1. NULLs are ignored (behaves as empty string)

  2. BLOBs, if necessary, are transliterated to the character set of the first argument and their contents are appended to the result

  3. 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

  1. 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
See also

Concatenation Operator, LIST(), RDB$BLOB_UTIL

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
See also

[fblangref50-scalarfuncs-bit-length], [fblangref50-scalarfuncs-octet-length]

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

  1. Hashing x with the CRC32 algorithm

    select hash(x using crc32) from y;

  2. 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
See also

[fblangref50-scalarfuncs-datediff], Operations Using Date and Time Values

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))
See also

[fblangref50-scalarfuncs-dateadd], Operations Using Date and Time Values

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 SMALLINTs 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).

See also

[fblangref50-scalarfuncs-bin-or], [fblangref50-scalarfuncs-bin-xor]

BIN_NOT()

Bitwise NOT

Result type

integer type matching the argument

Note

SMALLINT result is returned only if all the arguments are explicit SMALLINTs 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.

See also

[fblangref50-scalarfuncs-bin-or], [fblangref50-scalarfuncs-bin-xor] and others in this set.

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 SMALLINTs 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).

See also

[fblangref50-scalarfuncs-bin-and], [fblangref50-scalarfuncs-bin-xor]

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·2b.

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/2b.

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 SMALLINTs 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).

See also

[fblangref50-scalarfuncs-bin-and], [fblangref50-scalarfuncs-bin-or]

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)"
See also

[fblangref50-scalarfuncs-uuid-to-char], [fblangref50-scalarfuncs-gen-uuid]

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)
See also

[fblangref50-scalarfuncs-uuid-to-char], [fblangref50-scalarfuncs-char-to-uuid]

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'
See also

[fblangref50-scalarfuncs-char-to-uuid], [fblangref50-scalarfuncs-gen-uuid]

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);
See also

NEXT VALUE FOR, CREATE SEQUENCE (GENERATOR)

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
See also

[fblangref50-scalarfuncs-iif], [fblangref50-scalarfuncs-nullif], CASE

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
See also

CASE, [fblangref50-scalarfuncs-decode]

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.

See also

[fblangref50-scalarfuncs-coalesce], [fblangref50-scalarfuncs-decode], [fblangref50-scalarfuncs-iif], CASE