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 Procedural SQL (PSQL) StatementsAggregate Functions 

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.

docnext count = 31

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