Use the CASE and NULLIF expressions for conditional expressions in Derby.
NULLIF ( L, R )The NULLIF expression is very similar to the CASE expression. For example:
NULLIF(V1,V2)is equivalent to the following CASE expression:
CASE WHEN V1=V2 THEN NULL ELSE V1 END
You can place a CASE expression anywhere an expression is allowed. It chooses an expression to evaluate based on a boolean test.
CASE WHEN booleanExpression THEN thenExpression [ WHEN booleanExpression THEN thenExpression ]... ELSE elseExpression END
ThenExpression and elseExpression are both expressions that must be type-compatible. For built-in types, this means that the types must be the same or a built-in broadening conversion must exist between the types.
-- returns 3 VALUES CASE WHEN 1=1 THEN 3 ELSE 4 END
-- returns 7 VALUES CASE WHEN 1 = 2 THEN 3 WHEN 4 = 5 THEN 6 ELSE 7 END