数据库入门脚本

create table Users
(
id int primary key,
username varchar(32) unique ,
address varchar(255),
orderid int
)
orderid 关联 Order 的 id

create table Orders
(
id int primary key,
ordername varhchar(32)
)

select * from Users ,Orders

select * from Users where id >5 and id<10
或者
selet * from Users where id in(5,10)
或者
select * from Users where id between 5 and 10

模糊查询
select * from Users where username like '%a'
select * from Users where username like 'a%'
select * from Users where username like '%a%'

内连接
select * from Users u inner join Orders o on u.orderid=o.id

做外链接 做表为主 如果右表 没有数据 用null代替
select * from Users u left join Orders o on u.orderid=o.id

右外链接 右表为主 如果右表 没有数据 用null代替
select * from Users u right join Orders o on u.orderid=o.id

delete from Users where id=1

update Users set username ='王磊' where id=1

insert into Users values('王磊')