创建数据库
use master
go
create database stuuuuu
//删除数据库
if db_id ('$$$') is not null
Drop database [$$$]
go
//新建表
USE [studyTest]
GO
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
CREATE TABLE [dbo].[Table_1](
[id] [int] NULL,
[name] [varchar](10) NULL
) ON [PRIMARY]
GO
//删除表
USE [studyTest]
GO
IF EXISTS (SELECT * FROM sys.objects WHERE object_id = OBJECT_ID(N'[dbo].[Table_1]') AND type in (N'U'))
DROP TABLE [dbo].[Table_1]
GO
插入 insert into aaa ( name ) values ('asd')
/* 更新*/
update aaa set name='我是' where id=1
/* 删除*/
delete aaa where id =1
go
/*条件查询*/
select id as '标识',
name as '姓名',
score as 分数
from aaa where score >20 and score <90
/* score >20 and score <90 可以替换成between 50 and 90
不为空条件 where score is not null*/
/*百分比查询数据*/
select top(50) percent id as '标识',
name as '姓名',
score as 分数
from aaa where score >20 and score <90
caseWhen判断
select name,score ,case when score >20 and score<50 then '不及格'
when score>60 then '好'
else '零'
end as '等级'
from aaa order by score asc
// in
select name,score from aaa where id in (2)
// like
select name,score from aaa where name like 'a%'
// with
with tt as (select name,score from aaa where name like 'a%')
select * from tt
//distinct
select distinct id from aaa
//order by 升序 asc 降序 desc
select *from aaa order by score asc
//聚合group by
select name,sum(score) scoresum from aaa group by name
//左连接 left inner right full join
select *from Company c left join SysUser s on c.Id=s.CompanyId and .....
// union unionall 把结构相同的表合并,union可以去重, unionall 不会去重
//递归查询
with con(id,meanname,parentid,le) as
(
select id,meanname,parentid,le from meaninfo where id=1
union all
select a.id .... , le = le+1 from meaninfo a join con a.parent = con.id
)
select id,meanname,parentid,le from con
数据类型
date 年月日3byte datetime 年月日时分秒8byte time 时分秒5byte
约束
主键约束，外键约束 ，非空约束，唯一约束，检查约束
存储过程
