sql2008百万级数据排除重复信息

--高性能排除重复
select userid from  table  where userid in ( 

select userid from ( 

select userid, row_number()over(partition by email order by userid ) num 

from table

) v where num <> 1 

)     

row_number() OVER (PARTITION BY COL1 ORDER BY COL2) 表示根据COL1分组，在分组内部根据 COL2排序

row_number() OVER (ORDER BY COL2) 表示根据COL2排序这样可以得到一个序号