Firebird Documentation Index → Firebird 2.0 Language Ref. Update → External functions (UDFs) → *nullif |
Library: fbudf
Added in: 1.0 (Win), 1.5 (Linux)
Better alternative: Internal function NULLIF()
Description: The four *nullif
functions – for integers, bigints, doubles and
strings, respectively – each return the first argument if it is not equal to the second. If
the arguments are equal, the functions return NULL
.
Result type: Varies, see declarations.
Syntax:
inullif (int1
,int2
) i64nullif (bigint1
,bigint2
) dnullif (double1
,double2
) snullif (string1
,string2
)
As from Firebird 1.5, use of the internal function NULLIF is preferred.
These functions return NULL
when the second argument is
NULL
, even if the first argument is a proper value. This is a wrong
result. The NULLIF internal function doesn't have this bug.
i64nullif
and dnullif
will return wrong
and/or bizarre results if it is not 100% clear to the engine that each argument is of
the intended type (NUMERIC(18,0) or DOUBLE
PRECISION). If in doubt, cast them both explicitly to the declared type (see
declarations below).
Declarations:
DECLARE EXTERNAL FUNCTION inullif INT BY DESCRIPTOR, INT BY DESCRIPTOR RETURNS INT BY DESCRIPTOR ENTRY_POINT 'iNullIf' MODULE_NAME 'fbudf'DECLARE EXTERNAL FUNCTION i64nullif NUMERIC(18,4) BY DESCRIPTOR, NUMERIC(18,4) BY DESCRIPTOR RETURNS NUMERIC(18,4) BY DESCRIPTOR ENTRY_POINT 'iNullIf' MODULE_NAME 'fbudf'DECLARE EXTERNAL FUNCTION dnullif DOUBLE PRECISION BY DESCRIPTOR, DOUBLE PRECISION BY DESCRIPTOR RETURNS DOUBLE PRECISION BY DESCRIPTOR ENTRY_POINT 'dNullIf' MODULE_NAME 'fbudf'DECLARE EXTERNAL FUNCTION snullif VARCHAR(100) BY DESCRIPTOR, VARCHAR(100) BY DESCRIPTOR, VARCHAR(100) BY DESCRIPTOR RETURNS PARAMETER 3 ENTRY_POINT 'sNullIf' MODULE_NAME 'fbudf'
Firebird Documentation Index → Firebird 2.0 Language Ref. Update → External functions (UDFs) → *nullif |