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Provides an abbreviated CASE expression by comparing expressions.
NULLIF( expression-1, expression-2 )
expression-1 An expression to be compared.
expression-2 An expression to be compared.
NULLIF compares the values of the two expressions.
If the first expression equals the second expression, NULLIF returns NULL.
If the first expression does not equal the second expression, or if the second expression is NULL, NULLIF returns the first expression.
The NULLIF function provides a short way to write some CASE expressions.
SQL/2003 Core feature.
The following statement returns the value a:
SELECT NULLIF( 'a', 'b' );
The following statement returns NULL.
SELECT NULLIF( 'a', 'a' );