DELIMITER $$

CREATE
    /*mysql嵌套if演示*/
    PROCEDURE `pfmalls`.`pfm_proc_test`
    (
	a INT,   
	b INT
    )
   BEGIN   
	DECLARE c INT;   
	IF a IS NULL THEN   
		SET a = 0;
	ELSEIF a > 10 THEN
		IF a < 15 THEN
			SET a = 20;
		ELSEIF a > 10 THEN
			SET a = 10;
		END IF;
	ELSE #严重注意 else后面不用跟then 
		IF a > 30 THEN
			SET a = 30;
		ELSE
			SET a = 40;
		END IF;
		
		#set a = 30;
	END IF;  
	 
	IF b IS NULL THEN   
		SET b = 0;   
	END IF;  
	SET c = a + b;   
	SELECT c AS SUM;   
    END$$

DELIMITER ;

/*执行: call(10,20);*/