ตอนที่ 15 : การสร้าง Function บน MySQL Database (MySQL : Function)

CREATE FUNCTION function_name(Parameter1 DataType(size), Parameter2 DataType(size))
	RETURNS DataType(size)
BEGIN
	RETURN Variable;
END

DROP FUNCTION IF EXISTS getDiffAmount;

DELIMITER //
CREATE FUNCTION getDiffAmount(pAmt1 DECIMAL(18,2),pAmt2 DECIMAL(18,2))
	RETURNS DECIMAL(18,2)
BEGIN
	DECLARE diffAmt DECIMAL(18,2);
	  
	SET diffAmt = pAmt1 - pAmt2;
		
	RETURN diffAmt;
END //
DELIMITER ;

SELECT getDiffAmount(2000, 500) As DiffAmt

SELECT *, getDiffAmount(BUDGET,USED) AS DiffAmount FROM customer