MySQL---存储过程 及 条件语句、循环语句
存储过程
存储过程是一个SQL语句集合，当主动去调用存储过程时，其中内部的SQL语句会按照逻辑执行。
1、创建存储过程
1 -- 创建存储过程
2
3 delimiter //
4 create procedure p1()
5 BEGIN
6 select * from t1;
7 END//
8 delimiter ;
9
10
11
12 -- 执行存储过程
13
14 call p1()
1 注：
2 delimiter // 设置mysql的截止符为“//”
3
4 delimiter ;
对于存储过程，可以接收参数，其参数有三类：
- in 仅用于传入参数用
- out 仅用于返回值用
- inout 既可以传入又可以当作返回值
1 -- 创建存储过程
2 delimiter \\
3 create procedure p1(
4 in i1 int,
5 in i2 int,
6 inout i3 int,
7 out r1 int
8 )
9 BEGIN
10 DECLARE temp1 int;
11 DECLARE temp2 int default 0;
12
13 set temp1 = 1;
14
15 set r1 = i1 + i2 + temp1 + temp2;
16
17 set i3 = i3 + 100;
18
19 end\\
20 delimiter ;
21
22 -- 执行存储过程
23 set @t1 =4;
24 set @t2 = 0;
25 CALL p1 (1, 2 ,@t1, @t2);
26 SELECT @t1,@t2;
1 delimiter //
2 create procedure p1()
3 begin
4 select * from v1;
5 end //
6 delimiter ;
1 delimiter //
2 create procedure p2(
3 in n1 int,
4 inout n3 int,
5 out n2 int,
6 )
7 begin
8 declare temp1 int ;
9 declare temp2 int default 0;
10
11 select * from v1;
12 set n2 = n1 + 100;
13 set n3 = n3 + n1 + 100;
14 end //
15 delimiter ;
1 delimiter \\
2 create PROCEDURE p1(
3 OUT p_return_code tinyint
4 )
5 BEGIN
6 DECLARE exit handler for sqlexception
7 BEGIN
8 -- ERROR
9 set p_return_code = 1;
10 rollback;
11 END;
12
13 DECLARE exit handler for sqlwarning
14 BEGIN
15 -- WARNING
16 set p_return_code = 2;
17 rollback;
18 END;
19
20 START TRANSACTION;
21 DELETE from tb1;
22 insert into tb2(name)values('seven');
23 COMMIT;
24
25 -- SUCCESS
26 set p_return_code = 0;
27
28 END\\
29 delimiter ;
1 delimiter //
2 create procedure p3()
3 begin
4 declare ssid int; -- 自定义变量1
5 declare ssname varchar(50); -- 自定义变量2
6 DECLARE done INT DEFAULT FALSE;
7
8
9 DECLARE my_cursor CURSOR FOR select sid,sname from student;
10 DECLARE CONTINUE HANDLER FOR NOT FOUND SET done = TRUE;
11
12 open my_cursor;
13 xxoo: LOOP
14 fetch my_cursor into ssid,ssname;
15 if done then
16 leave xxoo;
17 END IF;
18 insert into teacher(tname) values(ssname);
19 end loop xxoo;
20 close my_cursor;
21 end //
22 delimter ;
1 delimiter \\
2 DROP PROCEDURE IF EXISTS proc_sql \\
3 CREATE PROCEDURE proc_sql ()
4 BEGIN
5 declare p1 int;
6 set p1 = 11;
7 set @p1 = p1;
8
9 PREPARE prod FROM 'select * from tb2 where nid > ?';
10 EXECUTE prod USING @p1;
11 DEALLOCATE prepare prod;
12
13 END\\
14 delimiter ;
2、删除存储过程
1 drop procedure proc_name;
3、执行存储过程
1 -- 无参数
2 call proc_name()
3
4 -- 有参数，全in
5 call proc_name(1,2)
6
7 -- 有参数，有in，out，inout
8 set @t1=0;
9 set @t2=3;
10 call proc_name(1,2,@t1,@t2)
1 #!/usr/bin/env python
2 # -*- coding:utf-8 -*-
3 import pymysql
4
5 conn = pymysql.connect(host='127.0.0.1', port=3306, user='root', passwd='123', db='t1')
6 cursor = conn.cursor(cursor=pymysql.cursors.DictCursor)
7 # 执行存储过程
8 cursor.callproc('p1', args=(1, 22, 3, 4))
9 # 获取执行完存储的参数
10 cursor.execute("select @_p1_0,@_p1_1,@_p1_2,@_p1_3")
11 result = cursor.fetchall()
12
13 conn.commit()
14 cursor.close()
15 conn.close()
16
17
18 print(result)
条件语句
1 delimiter \\
2 CREATE PROCEDURE proc_if ()
3 BEGIN
4
5 declare i int default 0;
6 if i = 1 THEN
7 SELECT 1;
8 ELSEIF i = 2 THEN
9 SELECT 2;
10 ELSE
11 SELECT 7;
12 END IF;
13
14 END\\
15 delimiter ;
循环语句
1 delimiter \\
2 CREATE PROCEDURE proc_while ()
3 BEGIN
4
5 DECLARE num INT ;
6 SET num = 0 ;
7 WHILE num < 10 DO
8 SELECT
9 num ;
10 SET num = num + 1 ;
11 END WHILE ;
12
13 END\\
14 delimiter ;
1 delimiter \\
2 CREATE PROCEDURE proc_repeat ()
3 BEGIN
4
5 DECLARE i INT ;
6 SET i = 0 ;
7 repeat
8 select i;
9 set i = i + 1;
10 until i >= 5
11 end repeat;
12
13 END\\
14 delimiter ;
1 BEGIN
2
3 declare i int default 0;
4 loop_label: loop
5
6 set i=i+1;
7 if i<8 then
8 iterate loop_label;
9 end if;
10 if i>=10 then
11 leave loop_label;
12 end if;
13 select i;
14 end loop loop_label;
15
16 END
