Internal functions and directives

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Internal functions and directives

Internal functions

The following built-in functions return NULL if at least one argument is NULL:

Notes 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.

FIRST, SKIP and ROWS

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:

This new Firebird 2 directive returns an empty set if any argument is NULL:

Side note: ROWS complies with the SQL standard. In new code, use ROWS, not FIRST and SKIP.

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