SQL 判断列数据重复,谢谢

Question

同一张表，判断A列是否有重复的值，如果有，则判断B列中的时间，取时间最大的一条，怎么写语句？

Answer 1

 if exists (select A from 测试表 group by A having count(A)>1)

select A,max(B) from 测试表 group by A having count(A)>1

Answer 2

http://blog.sina.cn/dpool/blog/s/blog_82b0c72f01016gqg.html?
一些查找，去除重复的方法，你自己扩充到你的要求上吧

Answer 3

最简单的自己union自己，一个select a一个select b
再group

Answer 4

Select B from table where A in (select A from table group by A having count (A)>1)

Answer 5

if exists (select A from table group by A having count(A)>1){select A,max(B) from table group by A having count(A)>1}