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firebird-mirror/doc/sql.extensions/README.nullif
skywalker 47fc3374d0 documentation for new sql clauses case, coalesce and nullif
contributed by Arno Brinkman <firebird@abvisie.nl>
2002-08-08 23:33:23 +00:00

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Function:
Speicify an alternative value for a column to return when it has a NULL
value.
Author:
Arno Brinkman <firebird@abvisie.nl>
Format:
<case abbreviation> ::=
NULLIF <left paren> <value expression> <comma> <value expression> <right paren>
Syntax Rules:
1) NULLIF (V1, V2) is equivalent to the following <case specification>:
CASE WHEN V1 = V2 THEN NULL ELSE V1 END
Examples:
A)
UPDATE PRODUCTS
SET STOCK = NULLIF(STOCK,0)