MySQL存储过程传参之in,out,inout参数用法_MySQL

DELIMITER $$
CREATE PROCEDURE p1(IN num INT)
BEGIN
 DECLARE i INT DEFAULT 0;
 DECLARE total INT DEFAULT 0;
 WHILE i<=num DO
 SET total := i + total;
 SET i := i+1;
 END WHILE;
 SELECT total;
END$$

CREATE PROCEDURE p2(OUT num INT)
BEGIN
 SELECT num AS num_1;
 IF (num IS NOT NULL) THEN
 SET num = num + 1;
 SELECT num AS num_2;
 ELSE
 SELECT 1 INTO num;
 END IF;
 SELECT num AS num_3;
END$$
SET @num = 10$$
CALL p2(@num)$$
SELECT @num AS num_out$$

CREATE PROCEDURE p3(INOUT age INT)
BEGIN
 SET age := age + 20;
END$$
set @currage =18$$
call p3(@currage)$$
select @currage$$