Parameters or Arguments: selector - an optional expression, whose value is used to select one of several alternatives. condition_1, ... condition_n - Evaluated in the order listed. Once a condition is found to be true, the CASE function will return the result and not evaluate the conditions any further. result_1, ... result_n - The value returned once a condition is found to be true.
CASE [ selector ] WHEN condition_1 THEN result_1 ... WHEN condition_n THEN result_n ELSE result END
In this CASE function example, the expression is quantity whose value would be compared to each of the conditions until one is met. Then the corresponding value would be returned by the CASE function.
SELECT supplier_id, CASE quantity WHEN > 10 THEN 'The quantity is greater than 10' WHEN = 10 THEN 'The quantity is 10' ELSE 'The quantity is something else' END FROM suppliers;
In this CASE function example, an expression has not been included so each condition is individually evaluated and can be completely different and unique. When a condition is met, the corresponding value would be returned.
SELECT CASE WHEN a < b THEN 1 WHEN supplier_type = 'clothing' THEN 2 ELSE 3 END FROM suppliers;