存储过程

create procedure 存储过程名(
    out 参数名1 DECIMAL(8,2),
    out 参数名2 VARCHAR(50)
)

BEGIN
    select AVG(age) into 参数名1  from `user` ;
  select `name`  from `user`  where `id`=‘3‘ into 参数名2; 
END

create procedure proce_select_name(
    out temp_age DECIMAL(8,2),
    out temp_name VARCHAR(50)
)

BEGIN
    select AVG(age) into temp_age  from `user` ;
  select `name`  from `user`  where `id`=‘3‘ into temp_name; 
END


CALL proce_select_name(@age,@name);
select @age,@name;

-- 带输入输出参数
create PROCEDURE proce_get_hobby_for_id(
    IN set_id int ,
    OUT get_hobby VARCHAR(50)
)

BEGIN
    select hobby from `user` 
    where  id =  set_id 
    into get_hobby;
END

drop PROCEDURE if EXISTS proce_get_hobby_for_id

CALL proce_get_hobby_for_id(1,@hobby);
select @hobby


-- 智能存储过程。。

create procedure proce_age_for_id
(
    IN set_id int,
    IN is_bool BOOLEAN,
    OUT    get_age INT
)

BEGIN
    DECLARE temp_age int; -- 用DECLARE关键字定义了一个int类型的temp_age局部变量
    DECLARE extra_age int DEFAULT 5;
    
    select age from `user` where id = set_id INTO temp_age;
    
    --if 检查is_bool是否为真,如果为真就执行.  if 语句还支持elseif ,else字句. 
    if is_bool  THEN
        select temp_age + extra_age INTO temp_age;
    end if;

    select temp_age INTO get_age;
    
END;

CALL proce_age_for_id(3,0,@scal_age);
select @scal_age;

CREATE TABLE `user` (
  
`id` int(11) NOT NULL AUTO_INCREMENT,
 
 `name` varchar(50) DEFAULT NULL,
  
`age` int(3
) 
DEFAULT NULL,
  `hobby` varchar(100) DEFAULT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=4 DEFAULT CHARSET=gbk