Python全栈之路-MySQL（四）

1 上下连表

union # 自动去重
union # 不去重
select sid,sname from student 
union
select sid,teacher from teacher

select sid,sname from student 
union all
select sid,teacher from student

2 基于角色的权限管理

用户信息表
id username pwd role_id

权限表
id privilege_name

角色表
id role_name

角色权限管理
id privilege_id role_id

1.基于角色的权限管理
2.需求分析


http://www.cnblogs.com/wupeiqi/articles/5713323.html

3 视图(虚拟表)

相当于给临时表起了个别名，方便日后使用

- 创建视图
create view v1 as select * from student where sid > 10;
- 使用视图
select * from v1;
- 修改视图
alter view v1 as select * from student where sid < 10;
- 删除视图
drop view v1; 

4 触发器(不常使用)

当对某张表做增删改操作时，可以使用触发器在操作前后自定义关联行为

1 插入前

CREATE TRIGGER tri_before_insert_tb1 BEFORE INSERT ON tb1 FOR EACH ROW
BEGIN
    ...
END

2 插入后

CREATE TRIGGER tri_after_insert_tb1 AFTER INSERT ON tb1 FOR EACH ROW
BEGIN
    ...
END

3 删除前

CREATE TRIGGER tri_before_delete_tb1 BEFORE DELETE ON tb1 FOR EACH ROW
BEGIN
    ...
END

4 删除后

CREATE TRIGGER tri_after_delete_tb1 AFTER DELETE ON tb1 FOR EACH ROW
BEGIN
    ...
END

5 更新前

CREATE TRIGGER tri_before_update_tb1 BEFORE UPDATE ON tb1 FOR EACH ROW
BEGIN
    ...
END

6 更新后

CREATE TRIGGER tri_after_update_tb1 AFTER UPDATE ON tb1 FOR EACH ROW
BEGIN
    ...
END

实例：

delimiter //
create trigger t1 before insert on student for each row
begin
    insert into teacher(tname) values('teacher01');
end
delimiter ;


delimiter //
CREATE TRIGGER tri_before_insert_tb1 BEFORE INSERT ON tb1 FOR EACH ROW
BEGIN

IF NEW.NAME == 'alex' THEN
    INSERT INTO tb2 (NAME)
VALUES
    ('aa')
END
END//
delimiter ;

delimiter //
CREATE TRIGGER tri_after_insert_tb1 AFTER INSERT ON tb1 FOR EACH ROW
BEGIN
    IF NEW.num = 666 THEN
        INSERT INTO tb2 (NAME)
        VALUES
            ('666'),
            ('666') ;
    ELSEIF NEW.num = 555 THEN
        INSERT INTO tb2 (NAME)
        VALUES
            ('555'),
            ('555') ;
    END IF;
END//
delimiter ;

NEW 代指新数据 insert操作
OLD 代指老数据 delete update 

5 函数

• 内置函数：max min avg sum count curdate
• 自定义函数

内置函数实例：

blog 文章按月分组，显示月份和文章数
id  title ctime
1   t1    2019-11-10 11:10
2   t2    2019-11-10 13:10
3   t3    2019-12-10 14:10
4   t4    2019-12-10 16:10

select ctime,count(1) from blog group by ctime
select DATA_FORMAT(ctime,"%Y-%m),count(1) from blog group by DATA_FORMAT(ctime,"%Y-%m) 


delimiter \
create function f1(
    i1 int,
    i2 int)
returns int
BEGIN
    declare num int;
    set num = i1 + i2;
    return(num);
END \
delimiter ;

select f1(1,100);

6 存储过程

保存在mysql服务端上的一个别名 => 一坨SQL语句

简单的存储过程

delimiter //
create procedure p1()
BEGIN
    select * from student;
    insert into teacher(tname) values ('teacher02');
END //
delimiter ;
call p1();

# pymysql执行存储过程
cursor.callproc('p1')
result = cursor.fetchall()
print(result)

传参数的存储过程（in out inout 三种参数类型）

参数in 传给函数内部使用 
delimiter //
create procedure p2(
    in n1 int,
    in n2 int
)
BEGIN
    select * from student where sid > n1;
    insert into teacher(tname) values ('teacher02');
END //
delimiter ;
call p2(5,10);

# pymysql执行存储过程
cursor.callproc('p2',(5,10))
result = cursor.fetchall()
print(result)

参数out 返回给外面使用
delimiter //
create procedure p3(
    in n1 int,
    out n2 int
)
BEGIN
    set n2 = 123123;
    select * from student where sid > n1;
    insert into teacher(tname) values ('teacher02');
END //
delimiter ;
set @v1 = 0; -- session级别全局变量
call p3(5,@v1); -- 返回值赋给@v1
select @v1;

# pymysql执行存储过程
cursor.callproc('p3',(5,10))
result = cursor.fetchall()
print(result)
cursor.execute('select @_p3_0,@_p3_1')
result = cursor.fetchall()
print(result)

参数inout：既能传进去使用，也能返回来使用

支持事务的存储过程
delimiter \
create PROCEDURE p5(
    OUT p_return_code tinyint
)
BEGIN 
  DECLARE exit handler for sqlexception 
  BEGIN 
    -- ERROR 
    set p_return_code = 1; 
    rollback; 
  END; 
 
  DECLARE exit handler for sqlwarning 
  BEGIN 
    -- WARNING 
    set p_return_code = 2; 
    rollback; 
  END; 
 
  START TRANSACTION; 
    DELETE from tb1;
    insert into tb2(name)values('seven');
  COMMIT; 
 
  -- SUCCESS 
  set p_return_code = 0; 
 
  END\
delimiter ;

存储过程里的游标
注意：游标的效率不高，当要对单独的表的每一行数据进行分门别类的操作时才使用游标

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(num) values(temp);
        end LOOP xxoo;
    close my_cursor;
end  //
delimiter ;
CALL p6()

动态执行SQL（防SQL注入）

delimiter \
CREATE PROCEDURE p7 (
    in nid int
)
BEGIN
    set @nid = nid;
    PREPARE prod FROM 'select * from student where sid > ?';
    EXECUTE prod USING @nid;
    DEALLOCATE prepare prod; 
END\
delimiter ;
call p7(10);

总结：

1.可传参 in out inout
    out或inout 可用来标识存储过程执行成功与否
2.pymysql操作
3.数据库相关操作
    - SQL语句 *****
    - 利用MySQL内部提供的功能