CASE Expressions

CASE expressions let you use IF... THEN... ELSE logic in expressions.

In a simple case expression, CASE searches for the first WHEN... THEN pair for which expr equals comparison_expr, then it returns return_expr. If none of the WHEN... THEN pairs meet this condition, and an ELSE clause exists, then CASE returns else_expr. Otherwise, CASE returns NULL.

In a searched CASE expression, CASE searches from left to right until it finds an occurrence of condition that is true, and then returns return_expr. If no condition is found to be true, and an ELSE clause exists, CASE returns else_expr. Otherwise, CASE returns NULL.