TOP的效率問題

select top 500 *from (select top 100 percent * from [dbo].[stg_address] a wherea.state_province_cd='NJ' order by a.created_dt) as sub

 

select top 500 *from [dbo].[stg_address] a where a.state_province_cd='NJ' order by a.created_dt

 

First query is better than second because TOP is useless if you have where clause onnon-index column

 

http://www.cnblogs.com/oneword/archive/2011/01/27/1946076.html