Firebird Documentation Index → Firebird Null Guide → Internal functions and directives |
The following built-in functions return NULL
if at least one
argument is NULL
:
CAST()
EXTRACT()
GEN_ID()
SUBSTRING()
UPPER()
LOWER()
BIT_LENGTH()
CHAR[ACTER]_LENGTH()
OCTET_LENGTH()
TRIM()
In 1.0.0, EXTRACT from a NULL
date would
crash the server. Fixed in 1.0.2.
If the first argument to GEN_ID is a valid generator name and
the second argument is NULL
, the named generator keeps its current
value.
In versions up to and including 2.0, SUBSTRING results are
sometimes returned as “false emptystrings”. These strings are in fact
NULL
, but are described by the server as non-nullable. Therefore,
most clients show them as empty strings. See the bugs list for a detailed description.
The following two directives crash a Firebird 1.5.n or
lower server if given a NULL
argument. In Firebird 2, they treat
NULL
as the value 0:
FIRST
SKIP
This new Firebird 2 directive returns an empty set if any argument is
NULL
:
ROWS
Side note: ROWS complies with the SQL standard. In new code, use ROWS, not FIRST and SKIP.
Firebird Documentation Index → Firebird Null Guide → Internal functions and directives |