8.3String Functions

8.3.1ASCII_CHAR()

Available inDSQL, PSQL

Possible name conflictYES → Read details

Syntax

  |ASCII_CHAR (code)

Table 8.27ASCII_CHAR Function Parameter
ParameterDescription

code

An integer within the range from 0 to 255

Result typeCHAR(1) CHARACTER SET NONE

DescriptionReturns 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 correctly returns a character with ASCII code 0 here.

8.3.2ASCII_VAL()

Available inDSQL, PSQL

Possible name conflictYES → Read details

Syntax

  |ASCII_VAL (ch)

Table 8.28ASCII_VAL Function Parameter
ParameterDescription

ch

A string of the [VAR]CHAR data type or a text BLOB with the maximum size of 32,767 bytes

Result typeSMALLINT

DescriptionReturns 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. (A bug in Firebird 2.1 - 2.1.3 and 2.5.0 causes an error to be raised if any character in the string is multi-byte. This is fixed in versions 2.1.4 and 2.5.1.)

8.3.3BIT_LENGTH()

Available inDSQL, PSQL

Syntax

  |BIT_LENGTH (string)

Table 8.29BIT_LENGTH Function Parameter
ParameterDescription

string

An expression of a string type

Result typeINTEGER

DescriptionGives 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.

BLOB supportSince Firebird 2.1, this function fully supports text BLOBs of any length and character set.

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 alsoSection 8.3.9, “OCTET_LENGTH(), Section 8.3.4, “CHAR_LENGTH(), CHARACTER_LENGTH()

8.3.4CHAR_LENGTH(), CHARACTER_LENGTH()

Available inDSQL, PSQL

Syntax

  |  CHAR_LENGTH (string)
  || CHARACTER_LENGTH (string)

Table 8.30CHAR[ACTER]_LENGTH Function Parameter
ParameterDescription

string

An expression of a string type

Result typeINTEGER

DescriptionGives the length in characters of the input string.

Notes
  • 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.

  • BLOB support: Since Firebird 2.1, this function fully supports text BLOBs of any length and character set.

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 alsoSection 8.3.3, “BIT_LENGTH(), Section 8.3.9, “OCTET_LENGTH()

8.3.5HASH()

Available inDSQL, PSQL

Syntax

  |HASH (string)

Table 8.31HASH Function Parameter
ParameterDescription

string

An expression of a string type

Result typeBIGINT

DescriptionReturns a hash value for the input string. This function fully supports text BLOBs of any length and character set.

8.3.6LEFT()

Available inDSQL, PSQL

Syntax

  |LEFT (string, length)

Table 8.32LEFT Function Parameters
ParameterDescription

string

An expression of a string type

length

Integer expression. Defines the number of characters to return

Result typeVARCHAR or BLOB

DescriptionReturns the leftmost part of the argument string. The number of characters is given in the second argument.

  • 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 alsoSection 8.3.14, “RIGHT()

8.3.7LOWER()

Available inDSQL, ESQL, PSQL

Possible name conflictYES → Read details below

Syntax

  |LOWER (string)

Table 8.33LOWER Function ParameterS
ParameterDescription

string

An expression of a string type

Result type(VAR)CHAR or BLOB

DescriptionReturns the lower-case 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 OCTETS, the entire string is returned unchanged. Since Firebird 2.1 this function also fully supports text BLOBs of any length and character set.

Name Clash

Because LOWER is a reserved word, the internal function will take precedence even if the external function by that name has also been declared. To call the (inferior!) external function, use double-quotes and the exact capitalisation, as in "LOWER"(string).

Example

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

See alsoSection 8.3.18, “UPPER()

8.3.8LPAD()

Available inDSQL, PSQL

Possible name conflictYES → Read details

Syntax

  |LPAD (str, endlen [, padstr])

Table 8.34LPAD Function Parameters
ParameterDescription

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 (' ')

Result typeVARCHAR or BLOB

DescriptionLeft-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.

Note

In Firebird 2.1-2.1.3, all non-BLOB results were of type VARCHAR(32765), which made it advisable to cast them to a more modest size. This is no longer the case.

🛑
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.

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 alsoSection 8.3.15, “RPAD()

8.3.9OCTET_LENGTH()

Available inDSQL, PSQL

Syntax

  |OCTET_LENGTH (string)

Table 8.35OCTET_LENGTH Function Parameter
ParameterDescription

string

An expression of a string type

Result typeINTEGER

DescriptionGives 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, 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.

BLOB supportSince Firebird 2.1, this function fully supports text BLOBs of any length and character set.

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

See alsoSection 8.3.3, “BIT_LENGTH(), Section 8.3.4, “CHAR_LENGTH(), CHARACTER_LENGTH()

8.3.10OVERLAY()

Available inDSQL, PSQL

Syntax

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

Table 8.36OVERLAY Function Parameters
ParameterDescription

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

Result typeVARCHAR or BLOB

DescriptionOVERLAY() overwrites part of a string with another string. 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 simply 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.

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'

🛑
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 alsoSection 8.3.12, “REPLACE()

8.3.11POSITION()

Available inDSQL, PSQL

Syntax

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

Table 8.37POSITION Function Parameters
ParameterDescription

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

Result typeINTEGER

DescriptionReturns 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.

Notes
  • 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.

    Notice: A bug in Firebird 2.1 - 2.1.3 and 2.5.0 causes POSITION to always return 1 if substr is the empty string. This is fixed in 2.1.4 and 2.5.1.

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

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

🛑
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 alsoSection 8.3.16, “SUBSTRING()

8.3.12REPLACE()

Available inDSQL, PSQL

Syntax

  |REPLACE (str, find, repl)

Table 8.38REPLACE Function Parameters
ParameterDescription

str

The string in which the replacement is to take place

find

The string to search for

repl

The replacement string

Result typeVARCHAR or BLOB

DescriptionReplaces all occurrences of a substring in a 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.

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'

🛑
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 alsoSection 8.3.10, “OVERLAY(), Section 8.3.16, “SUBSTRING(), Section 8.3.11, “POSITION(), Section 8.3.4, “CHAR_LENGTH(), CHARACTER_LENGTH()

8.3.13REVERSE()

Available inDSQL, PSQL

Syntax

  |REVERSE (string)

Table 8.39REVERSE Function Parameter
ParameterDescription

string

An expression of a string type

Result typeVARCHAR

DescriptionReturns a string backwards.

Examples

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

Tip

This function comes in very handy 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');

8.3.14RIGHT()

Available inDSQL, PSQL

Possible name conflictYES → Read details

Syntax

  |RIGHT (string, length)

Table 8.40RIGHT Function Parameters
ParameterDescription

string

An expression of a string type

length

Integer. Defines the number of characters to return

Result typeVARCHAR or BLOB

DescriptionReturns the rightmost part of the argument string. The number of characters is given in the second argument.

  • This function supports text BLOBs of any length, but has a bug in versions 2.1 - 2.1.3 and 2.5.0 that makes it fail with text BLOBs larger than 1024 bytes that have a multi-byte character set. This has been fixed in versions 2.1.4 and 2.5.1.

  • 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 alsoSection 8.3.6, “LEFT(), Section 8.3.16, “SUBSTRING()

8.3.15RPAD()

Available inDSQL, PSQL

Changed in2.5 (backported to 2.1.4)

Possible name conflictYES → Read details

Syntax

  |RPAD (str, endlen [, padstr])

Table 8.41RPAD Function Parameters
ParameterDescription

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 (' ')

Result typeVARCHAR or BLOB

DescriptionRight-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.

Note

In Firebird 2.1-2.1.3, all non-BLOB results were of type VARCHAR(32765), which made it advisable to cast them to a more modest size. This is no longer the case.

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'

🛑
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.

See alsoSection 8.3.8, “LPAD()

8.3.16SUBSTRING()

Available inDSQL, PSQL

Changed in2.5.1

Syntax

  |SUBSTRING (str FROM startpos [FOR length])

Table 8.42SUBSTRING Function Parameters
ParameterDescription

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

Result typesVARCHAR or BLOB

DescriptionReturns a string’s substring starting at the given position, either to the end of the string or with a given length.

This function returns the substring starting at character position startpos (the first position 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.

In Firebird 1.x, startpos and length must be integer literals. In 2.0 and above they can be any valid integer expression.

Starting with Firebird 2.1, this function fully supports binary and text BLOBs of any length and character set. If str is a BLOB, the result is also a BLOB. For any other argument type, the result is a VARCHAR. Previously, the result type used to be CHAR if the argument was a CHAR or a string literal.

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'.

If any argument is NULL, the result is NULL.

🛑
Bugs
  • If str is a BLOB and the length argument is not present, the output is limited to 32767 characters. Workaround: with long BLOBs, always specify char_length(str) — or a sufficiently high integer — as the third argument, unless you are sure that the requested substring fits within 32767 characters.

    This bug has been fixed in version 2.5.1; the fix was also backported to 2.1.5.

  • An older bug in Firebird 2.0, which caused the function to return false emptystrings if startpos or length was NULL, was fixed.

Example

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

🛑
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.

See alsoSection 8.3.11, “POSITION(), Section 8.3.6, “LEFT(), Section 8.3.14, “RIGHT(), Section 8.3.4, “CHAR_LENGTH(), CHARACTER_LENGTH()

8.3.17TRIM()

Available inDSQL, PSQL

Syntax

  |TRIM ([<adjust>] str)
  | 
  |<adjust> ::=  {[<where>] [what]} FROM
  | 
  |<where> ::=  BOTH | LEADING | TRAILING

Table 8.43TRIM Function Parameters
ParameterDescription

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 (' ')

Result typeVARCHAR or BLOB

DescriptionRemoves leading and/or trailing spaces (or optionally other strings) from the input string. Since Firebird 2.1 this function fully supports text BLOBs of any length and character set.

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'

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

  • The substring to be removed, if specified, may not be bigger than 32767 bytes. However, if this substring is repeated at str's head or tail, the total number of bytes removed may be far greater. (The restriction on the size of the substring will be lifted in Firebird 3.)

🛑
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.

8.3.18UPPER()

Available inDSQL, ESQL, PSQL

Syntax

  |UPPER (str)

Table 8.44UPPER Function Parameter
ParameterDescription

str

An expression of a string type

Result type(VAR)CHAR or BLOB

DescriptionReturns the upper-case 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 OCTETS, the entire string is returned unchanged. Since Firebird 2.1 this function also fully supports text BLOBs of any length and character set.

Examples

  |select upper(_iso8859_1 'Débâcle')
  |from rdb$database
  |-- returns 'DÉBÂCLE' (before Firebird 2.0: 'DéBâCLE')
  | 
  |select upper(_iso8859_1 'Débâcle' collate fr_fr)
  |from rdb$database
  |-- returns 'DEBACLE', following French uppercasing rules

See alsoSection 8.3.7, “LOWER()