Python9-MySQL-MySQL存储过程-视图-触发器-函数-day45

视图：某个查询语句设置别名，日后方便使用
    CREATE VIEW v1 as SELECT * FROM student WHERE sid >10
    -创建：
        create view 视图名称 as SQL
        视图是虚拟的
    -修改
        alter view 视图名称  as SQL
    -删除
        drop view 视图名称

触发器：当对某张表做：增删改操作的时候，可以使用触发器自定义关联行为
# 插入前
CREATE TRIGGER tri_before_insert_tb1 BEFORE INSERT ON tb1 FOR EACH ROW
BEGIN
    ...
END
 
# 插入后
CREATE TRIGGER tri_after_insert_tb1 AFTER INSERT ON tb1 FOR EACH ROW
BEGIN
    ...
END
 
# 删除前
CREATE TRIGGER tri_before_delete_tb1 BEFORE DELETE ON tb1 FOR EACH ROW
BEGIN
    ...
END
 
# 删除后
CREATE TRIGGER tri_after_delete_tb1 AFTER DELETE ON tb1 FOR EACH ROW
BEGIN
    ...
END
 
# 更新前
CREATE TRIGGER tri_before_update_tb1 BEFORE UPDATE ON tb1 FOR EACH ROW
BEGIN
    ...
END
 
# 更新后
CREATE TRIGGER tri_after_update_tb1 AFTER UPDATE ON tb1 FOR EACH ROW
BEGIN
    ...
END
 
delimiter //
create TRIGGER t1 BEFORE INSERT on student for each ROW
BEGIN
    INSERT into teacher(tname) VALUES('tim');
END //
delimiter ;
--
 
INSERT INTO student(gender,class_id,sname) VALUES('女',2,'多长');
 
# NEW  代指新数据，在两张表中插入同样的数据
# OLD  代指老数据 在两张表中删除和更新同样的数据
-- delimiter //
-- create TRIGGER t1 BEFORE INSERT on student for each ROW
-- BEGIN
--     INSERT into teacher(tname) VALUES(NEW.sname);
-- END //
-- delimiter ;

内置函数：
    执行函数
        -- SELECT CURDATE()   #日期
        -- SELECT CHAR_LENGTH('st')  #字符串长度
        -- SELECT CONCAT('tim','ttutu','ssl')  #拼接
        时间格式化：
            SELECT DATE_FORMAT(date,format)
            SELECT DATE_FORMAT('2009-10-04', '%W %M %Y');
自定义函数：
        delimiter \\
        create function f1(
            i1 int,
            i2 int)
        returns int
        BEGIN
            declare num int;
            set num = i1 + i2;
            return(num);
        END \\
        delimiter ;

# 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。
#             保存在MySQL上的一个别名---》一坨SQL语句
 
方式一：
        Mysql：存储过程
        程序：调用存储过程
方式二：
        mysql：
        程序：sql语句
方式三：
    mysql
    程序：类和对象（sql语句）
 

delimiter //
CREATE PROCEDURE p1()
BEGIN
   SELECT * FROM student;
   INSERT into teacher(tname) VALUES("ct");
END //
delimiter ;
call p1()

import pymysql
conn = pymysql.connect(host='127.0.0.1',user='root',password='',database='homework666',charset='utf8')
cursor = conn.cursor()
cursor.callproc('p1',(12,2))
conn.commit()
result =  cursor.fetchall()
print(result)
cursor.close()
conn.close()

 1. 简单
   create procedure p1()
   BEGIN
      select * from student;
      INSERT into teacher(tname) values("ct");
   END
 
   call p1()
   cursor.callproc('p1')
2. 传参数（in,out,inout）
   delimiter //
   create procedure p2(
      in n1 int,
      in n2 int
   )
   BEGIN
 
      select * from student where sid > n1;
   END //
   delimiter ;
 
   call p2(12,2)
   cursor.callproc('p2',(12,2))
      3.参数out
         delimiter //
          create procedure p3(
              in n1 int,
              out n2 int
          )
          BEGIN
 
              set n2 = 123123;
              select * from student where sid > n1;
          END //
          delimiter ;
          set @v1=123;
          call p3(12,@v1);
          SELECT @v1;

import pymysql
conn = pymysql.connect(host='127.0.0.1',user='root',password='',database='homework666',charset='utf8')
cursor = conn.cursor()
cursor.callproc('p3',(12,2))
r1 =  cursor.fetchall()
print(r1)
cursor.execute('select @_p3_0,@_p3_1')
r2 =  cursor.fetchall()
print(r2)
cursor.close()
conn.close()

# 事务：
'''
delimiter \\
create PROCEDURE p5(
        OUT p_return_code tinyint
)
BEGIN
    DECLARE exit handler for sqlexception
    BEGIN
      -- ERROR
      set p_return_code = 1;
      rollback;
    END;
 
  START TRANSACTION;
    DELETE from tb1;
    insert into tb2(name)values('seven');
  COMMIT;
 
  -- SUCCESS
  set p_return_code =2;
 
END\\
delimiter ;
'''

# 游标
# 1、声明游标
# 2、获取A表中数据
#   my_cursor  select id,num form A
# 3、for  row_id,row_num in my_cursor:
#     检测循环是否还有数据，如果无数据
#     break
#     insert into B(num) values(row_id+row_num)
'''
delimiter //
create procedure p6()
begin
    declare row_id int; -- 自定义变量1
    declare row_num int; -- 自定义变量2
    DECLARE done INT DEFAULT FALSE;
    declare temp int;
 
    DECLARE my_cursor CURSOR FOR select id,num from A;
    DECLARE CONTINUE HANDLER FOR NOT FOUND SET done = TRUE;
 
    open my_cursor;
        xxoo: LOOP
            fetch my_cursor into row_id,row_num;
            if done then
                leave xxoo;
            END IF;
            set temp = row_id+row_num;
            insert into B(number) values(temp);
        end loop xxoo;
    close my_cursor;
end  //
delimter;
 
执行：
call p6()
'''

# 动态执行SQL（防SQL注入）
'''伪代码
delimiter //
create procedure p7(
    in tp1 varchar(225),
    in arg int
)
begin
    1.预检测某个东西 sql语句的合法性
    2.格式化tpl + arg
    3.执行SQL语句
    set @xo =arg
    PREPARE xxx FROM 'select * from student where sid > ?';
    EXECUTE xxx USING @xo;
    DEALLOCATE prepare prod;
end  //
delimter;
call p7("select * from tb where id >?",9)
'''
'''真实代码
delimiter \\
CREATE PROCEDURE p8 (
    in nid int
)
BEGIN
    set @nid = nid;
    PREPARE prod FROM 'select * from student where sid > ?';
    EXECUTE prod USING @nid;
    DEALLOCATE prepare prod;
END\\
delimiter ;
 
'''