数据库

命名习惯 数据库名.MyDB           表名.StuInfo

数据类型

int 整形

datetime 日期    getdate()

float 浮点

bit 布尔值

nvarchar(50) 变长  文本型

nvarchar(MAX) 备注

创建数据库

create database Library

创建表

create table Users

(

UID int primary key,

userName nvarchar(20) not null,

userPwd nvarchar(20) not null

)

查询语句

select * from StuInfo

select Sex,Age from StuInfo

select * from StuInfo where Sex=‘男‘ and (Age = 21 or Age=22)

select * from StuInfo where Sex=‘男‘ and Age in(21,22)

select * from StuInfo where Age>=10 and Age<=30

select * from StuInfo where Age between 20 and 25

select top 3 StuId,Sex from StuInfo where Sex=‘男‘ order by Age desc　　//desc倒序

select * from StuInfo where StuId like ‘%a%‘

select COUNT(*) as UserCount from StuInfo where Sex=‘男‘　　//count()统计

select MIN(Age) as MinAge from StuInfo

select MAX(Age) as MaxAge from StuInfo

select Avg(Age) as AvgAge from StuInfo　　//avg平均值

select * from StuInfo where Age>

(

select Avg(Age) as AvgAge from StuInfo

)

select COUNT(*) as AgeCount,Age from StuInfo Group by Age　　//分组

having COUNT(*)=1 order by Age

添加语句

insert into StuInfo values(‘11‘,‘吧‘,‘女‘,20,‘2005-7-30‘,‘‘,‘true‘,‘eqwe‘)

insert into StuInfo(StuId,Age) values(‘qq‘,11)

删除语句

delete StuInfo where StuId=‘qq‘

更新语句

update StuInfo set Sex=‘女‘ where ParenetId=1

联合查询

Left join      right join

数据库

原文：http://www.cnblogs.com/relstart/p/4893465.html