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

-- 创建存储过程  2 
delimiter //
create procedure p1()  5 BEGIN  6     select * from t1;  7 END//
delimiter ;  9 


-- 执行存储过程 13 
call p1()

注： 2     delimiter //     设置mysql的截止符为“//” 3 
    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

-- 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     
    set temp1 = 1; 14 
    set r1 = i1 + i2 + temp1 + temp2; 16     
    set i3 = i3 + 100; 18 
end\\ 20 delimiter ; 21 
-- 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;

delimiter //
 create procedure p1() 3  begin 4                         select * from v1; 5                     end //
                    delimiter ;

delimiter //
 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 
                        select * from v1; 12                         set n2 = n1 + 100; 13                         set n3 = n3 + n1 + 100; 14                     end //
                    delimiter ;

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                          
                          DECLARE exit handler for sqlwarning 14  BEGIN 15                             -- WARNING 16                             set p_return_code = 2; 17  rollback; 18  END; 19                          
 START TRANSACTION; 21                             DELETE from tb1; 22                             insert into tb2(name)values('seven'); 23  COMMIT; 24                          
                          -- SUCCESS 26                           set p_return_code = 0; 27                          
 END\\ 29                     delimiter ;

delimiter //
 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 

                        DECLARE my_cursor CURSOR FOR select sid,sname from student; 10                         DECLARE CONTINUE HANDLER FOR NOT FOUND SET done = TRUE; 11                         
 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  //
                    delimter ;

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 
    PREPARE prod FROM 'select * from tb2 where nid > ?'; 10  EXECUTE prod USING @p1; 11  DEALLOCATE prepare prod; 12 
END\\ 14 delimiter ;

2、删除存储过程

drop procedure proc_name;

3、执行存储过程

-- 无参数  2 call proc_name()  3 
-- 有参数，全in  5 call proc_name(1,2)  6 
-- 有参数，有in，out，inout  8 set @t1=0;  9 set @t2=3; 10 call proc_name(1,2,@t1,@t2)

#!/usr/bin/env python
# -*- coding:utf-8 -*-
import pymysql  4 
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
cursor.callproc('p1', args=(1, 22, 3, 4))  9 # 获取执行完存储的参数
cursor.execute("select @_p1_0,@_p1_1,@_p1_2,@_p1_3") 11 result = cursor.fetchall() 12 
conn.commit() 14 cursor.close() 15 conn.close() 16 

print(result)

条件语句

delimiter \\  2 CREATE PROCEDURE proc_if ()  3 BEGIN  4     
 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 
END\\ 15 delimiter ;

循环语句

delimiter \\  2 CREATE PROCEDURE proc_while ()  3 BEGIN  4 
 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 
END\\ 14 delimiter ;

delimiter \\  2 CREATE PROCEDURE proc_repeat ()  3 BEGIN  4 
 DECLARE i INT ;  6     SET i = 0 ;  7  repeat  8  select i;  9         set i = i + 1; 10         until i >= 5
 end repeat; 12 
END\\ 14 delimiter ;

BEGIN  2     
 declare i int default 0;  4  loop_label: loop  5         
        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 
END