Mysql视图触发器函数事务

Posted 2022-06-10 duhong0520

1. 视图
100个SQL：
88: v1

select .. from v1
select asd from v1
某个查询语句设置别名，日后方便使用

- 创建
create view 视图名称 as SQL

PS: 虚拟
- 修改
alter view 视图名称 as SQL

- 删除
drop view 视图名称;

2. 触发器

当对某张表做：增删改操作时，可以使用触发器自定义关联行为

insert into tb (....)

-- delimiter //
-- create trigger t1 BEFORE INSERT on student for EACH ROW
-- BEGIN
-- INSERT into teacher(tname) values(NEW.sname);
-- INSERT into teacher(tname) values(NEW.sname);
-- INSERT into teacher(tname) values(NEW.sname);
-- INSERT into teacher(tname) values(NEW.sname);
-- END //
-- delimiter ;
--

-- insert into student(gender,class_id,sname) values(‘女‘,1,‘陈涛‘),(‘女‘,1,‘张根‘);

-- NEW,代指新数据
-- OLD,代指老数据

3. 函数
def f1(a1,a2):
return a1 + a2

f1()
bin()

内置函数：
执行函数 select CURDATE();

blog
id title ctime
1 asdf 2019-11
2 asdf 2019-11
3 asdf 2019-10
4 asdf 2019-10


select ctime,count(1) from blog group ctime

select DATE_FORMAT(ctime, "%Y-%m"),count(1) from blog group DATE_FORMAT(ctime, "%Y-%m")
2019-11 2
2019-10 2


自定义函数(有返回值)：

delimiter \\
create function f1(
i1 int,
i2 int)
returns int
BEGIN
declare num int default 0;
set num = i1 + i2;
return(num);
END \\
delimiter ;

SELECT f1(1,100);

4. 存储过程
保存在mysql上的一个别名 => 一坨SQL语句

别名()

用于替代程序员写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）


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,
inout n2 int
)
BEGIN
set n2 = 123123;
select * from student where sid > n1;
END //
delimiter ;

set @v1 = 10;
call p2(12,@v1)
select @v1;

set @_p3_0 = 12
ser @_p3_1 = 2
call p3(@_p3_0,@_p3_1)
select @_p3_0,@_p3_1

cursor.callproc(‘p3‘,(12,2))
r1 = cursor.fetchall()
print(r1)

cursor.execute(‘select @_p3_0,@_p3_1‘)
r2 = cursor.fetchall()
print(r2)

=======> 特殊
a. 可传参： in out inout
b. pymysql

cursor.callproc(‘p3‘,(12,2))
r1 = cursor.fetchall()
print(r1)

cursor.execute(‘select @_p3_0,@_p3_1‘)
r2 = cursor.fetchall()
print(r2)

为什么有结果集又有out伪造的返回值？


delimiter //
create procedure p3(
in n1 int,
out n2 int 用于标识存储过程的执行结果 1,2
)
BEGIN
insert into vv(..)
insert into vv(..)
insert into vv(..)
insert into vv(..)
insert into vv(..)
insert into vv(..)
END //
delimiter ;

4. 事务


delimiter //
create procedure p4(
out status int
)
BEGIN
1. 声明如果出现异常则执行
set status = 1;
rollback;


开始事务
-- 由秦兵账户减去100
-- 方少伟账户加90
-- 张根账户加10
commit;
结束

set status = 2;


END //
delimiter ;

===============================
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 ;

5. 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(number) values(temp);
end loop xxoo;
close my_cursor;


end //
delimter ;

6. 动态执行SQL（防SQL注入）

delimiter //
create procedure p7(
in tpl varchar(255),
in arg int
)
begin
1. 预检测某个东西 SQL语句合法性
2. SQL =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)

===>

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 ;