SQLServer基本查询

条件查询

--1.比较运算符
select * from dbo.DepartMent where dID>=3
--2.确定集合谓词
select * from dbo.DepartMent where dID between 2 and 4
--3.确定范围谓词
select * from dbo.DepartMent where dID in( 2 , 4)
--4.字符匹配谓词
select * from dbo.DepartMent where dName like 'C%'
select * from dbo.DepartMent where dName not like '_#%'
--5.空值谓词
select * from dbo.DepartMent where dName IS null
select * from dbo.DepartMent where dName IS not null
--6.多重条件运算符
select * from dbo.DepartMent where dID =  2 or dID = 4
select * from dbo.DepartMent where dID =  2 and dID = 4

聚集函数介绍

--1.avg()
select avg(dID),dName from DepartMent group by dName
--2.count()
select count(dID),dName from DepartMent group by dName
--3.max()
select count(dID),dName from DepartMent group by dName
--4.min()
select min(dID),dName from DepartMent group by dName
--5.sum()
select sum(dID),dName from DepartMent group by dName

带top和distinct关键字的查询

Select  top 3 * from DepartMent
Select  distinct dName from DepartMent

附加子句查询

--Order by 字句
select * from dbo.DepartMent 
Order by dName desc
--Group by 字句
select dName from dbo.DepartMent 
Group by dName
--Having 字句
select COUNT(dID),dName from dbo.DepartMent 
Group by dName
Having COUNT(dID)>2
--Into 字句
select COUNT(dID) count,dName into #TmpTable
from dbo.DepartMent 
Group by dName
Having COUNT(dID)>2
--临时表(本次链接才有效)和基本表的区别
select * from  #TmpTable