How to write mysql stored procedure

You can use the CREATE PROCEDURE statement to create a stored procedure.

The database stored procedure syntax format is as follows:

CREATE PROCEDURE  过程名([[IN|OUT|INOUT] 参数名 数据类型[,[IN|OUT|INOUT] 参数名 数据类型…]]) [特性 ...] 过程体
DELIMITER //  
CREATE PROCEDURE myproc(OUT s int)    
BEGIN      
SELECT COUNT(*) INTO s FROM students;    
END    
//
DELIMITER ;

Example: Create a simple stored procedure

-- ----------------------------
-- Procedure structure for `proc_adder`
-- ----------------------------DROP PROCEDURE IF EXISTS `proc_adder`;
DELIMITER ;;CREATE DEFINER=`root`@`localhost` PROCEDURE `proc_adder`(IN a int, IN b int, OUT sum int)BEGIN
    #Routine body goes here...
 
    DECLARE c int;
    if a is null then set a = 0;
    end if;
  
    if b is null then set b = 0;
    end if;set sum  = a + b;END
;;
DELIMITER ;

Execute the above stored results and verify whether they are correct, as shown below

set @b=5;
call proc_adder(2,@b,@s);
select @s as sum;

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