MySQL GetCurrentRating(cid, m)

Question

Write a stored function GetCurrentRating(cid, m) which returns the current rating of model m by customer cid. If the cid has not rated m then this function should return NULL. This applies both in the case when cid has never rated m as well as in the case when cid has rated m but then cancelled their rating.

Answer 1

Post your attempt here

Answer 2

my attempt:

DELIMITER //
CREATE FUNCTION GetCurrentRating(cid, m) RETURNS INTEGER
DETERMINISTIC NO SQL READS SQL DATA
BEGIN
DECLARE v_CID_count INTEGER;

SELECT COUNT(*), Rating_of_model
INTO v_CID_count
FROM CUSTOMER C;
IF (
CID rated m then RETURN m_rating
else IF (
(CID NOT rated m then RETURN NULL)
else
CANCELLED
);

END//
DELIMITER ;