存储过程和存储函数

grade表:

select * from grade;
+----+------+--------+------+-------+-------+
| id | name | sexy   | age  | score | class |
+----+------+--------+------+-------+-------+
|  1 | a    | male   |   15 |    90 | A(1)  |
|  2 | b    | male   |   13 |    97 | A(1)  |
|  3 | c    | female |   15 |    79 | A(2)  |
|  4 | a    | female |   13 |   100 | B(1)  |
|  5 | d    | male   |   16 |    89 | B(2)  |
|  6 | e    | male   |   16 |    97 | B(2)  |
|  7 | f    | female |   15 |    93 | B(3)  |
|  8 | g    | female |   13 |    88 | C(1)  |
|  9 | h    | male   |   14 |    91 | C(2)  |
+----+------+--------+------+-------+-------+

 创建存储过程p_grade

delimiter &&
create procedure p_grade(in g_id int,out g_name varchar(20))
begin
declare g_score varchar(20);
select score into g_score from grade where id = g_id;
select name into g_name from grade where id = g_id;
select g_score;
end
&&
delimiter ;

call p_grade(1,@n);
+---------+
| g_score |
+---------+
| 90      |
+---------+

select @n;
+------+
| @n   |
+------+
| a    |
+------+

 1.参数g_name的作用范围是begin...end之间

2.declare声明的变量作用范围是begin...end之间

3.declare必须在所有set前面，即使是变量g_name,也必须在所有declare之后赋值。

4.declare可以声明多个变量，但是多个变量的类型必须一致。

　　正确语法:declare a,b,c int default 10;

　　错误语法: declare a int,b int,c int;

5.sql语句中为了给g_score和g_name赋值，使用了两条select语句。简洁写法如下

 　　select score,name into g_score,g_name from grade where id = g_id;