--聚合函数
select SUM(age)as 总和 from dbo.student
select AVG(age) 平均 from dbo.student
select max(age) 最大 from dbo.student
select min(age) 最小 from dbo.student
select count(*) 数量 from dbo.student
--模糊查询
select * from dbo.student where age IS null--查unll
select * from dbo.student where age IS not null --查非空
select * from dbo.student where address like '你%'--模糊查询
select * from dbo.student where stuID between 2 and 4
select * from dbo.student where address in ('你妹','11')
