sql语法查询一段时间的数据

---建表

create table qss
(shhijian datetime ,
 qian int)
go

--插入数据
 insert into qss values('2007-1-1 10:00:23' ,          8 )
 insert into qss values('2007-1-1 10:01:24' ,          4 )
insert into qss values('2007-1-1 10:05:00' ,          2 ) 
 insert into qss values('2007-1-1 10:06:12' ,          3 )
insert into qss values('2007-1-1 10:08:00' ,          1 )
insert into qss values('2007-1-1 10:12:11' ,          5 )
go    

---查询1个月内数据

--语法1
select * from qss where shhijian>dateadd(day,-30,getdate()) 
---语法2
select * from qss   where datediff(day,shhijian,getdate()) >=31