Mysql事项,视图,函数,触发器命令(详解)

//修改表的引擎
alter table a engine=myisam;
//开启事务
begin;
//关闭自动提交
set autocommit=0;
//扣100
update bank set money=money-100 where bid=1;
//回滚，begin开始的所有sql语句操作
rollback;

//开启事务
begin;
//关闭自动提交
set autocommit=0;
//扣100
update bank set money=money-100 where bid=1;
//加100
update bank set money=money+100 where bid=2;
//提交
commit;

$dsn = "mysql:host=127.0.0.1;dbname=c58";
try {
  //通过pdo连接数据库
  $pdo = new Pdo($dsn,'root','');
  //把错误设置成异常模式，才能try catch接收
  $pdo->setAttribute(PDO::ATTR_ERRMODE,PDO::ERRMODE_EXCEPTION);
  //设置字符集
  $pdo->query("SET NAMES utf8");
  //开启事务
  $pdo->query("BEGIN");
  //关闭自动提交
  $pdo->query("SET AUTOCOMMIT=0");
  //转账
  //扣掉100
  $pdo->exec('UPDATE bank SET money=money-100 WHERE bid=1');
  //加上100
  $pdo->exec('UPDATE bank SET money=money+100 WHERE bid=2');
  //提交
  $pdo->query('COMMIT');
} catch (PDOException $e) {
  $pdo->query('ROLLBACK');
  echo $e->getMessage();
}

//1.创建视图
create view bankview as select bid,bname from bank;
//2.查看视图
show table status where comment='VIEW';
//3.修改视图
alter view bankview as select bid from bank;
//4.删除视图
drop view bankview;

//更变边界符
\d $

//创建存储过程
create procedure get_bid(inout n char(20) charset utf8)
begin
  select bid from bank where name=n;
end
$

//调用
set @name='震'$
call get_bid(@name)$

//存储过程作业
//1. 创建删除班级的存储过程
//2. 实现删除班级时一并删除此班级中的学生
//3. 调用方式call del_class(1);
//创建表
create table class(
  cid int unsigned primary key auto_increment,
  cname char(20) not null default ''
);
create table stu(
  sid int unsigned primary key auto_increment,
  sname char(20) not null default '',
  cid int unsigned not null default 0
);
\d $
create procedure del_class(inout id smallint)
begin
  delete from class where cid=id;
  delete from stu where cid=id;
end
$
set @id=1$
call del_class(@id)$

//1.in(

输出外面传入的值，不能改变外面传入的值) create procedure a(in id int) begin select id; set id=100; end $ //2.out(不可以输出外面传入的值，能改变外面传入的值) create procedure b(out id int) begin select id; set id=100; end $ //3.inout（综合上述两种情况） create procedure insert_data(in num int) begin while num > 0 do insert into class set cname=num; set num = num - 1; end while; end $ //查看状态 show procedure status; //删除get_bid这个存储过程 drop procedure get_bid;

//创建
create function hello(s char(20) charset utf8)
returns char(50)
reads sql data
begin
  return concat('hello ',s,' !');
end
$

//调用
select hello('hdw')$
+--------------+
| hello('hdw') |
+--------------+
| hello hdw ! |
+--------------+

//删除
drop function hello$

//创建存储函数
create function getcid(n char(20) charset utf8)
returns int
reads sql data
begin
  return (select cid from stu where sname=n);
end
$
//存储函数可以用在sql语句中
select cname from class where cid=getcid('小猫')$

//删除班级自动触发删除学生
create trigger del_class_stu after delete on class
for each row
begin
  delete from stu where cid=old.cid;
end
$

//触发器作业
创建文章表含标题、作者、发布时间字段
如果只添加了标题,发布时间字段自动设置为当前时间,
作者字段设置为123网
\d $
create trigger this_name before insert on this_table for each row
begin
if new.uname is null then
set new.uname='123';
end if;
if new.timer is null then
set new.timer=unix_timestamp(now());
end if;
end
$

//查询已有触发器
show triggers;