select * from (select a.* row_number() over(partition by a.task_type,to_char(a.oper_time,‘yyyymmdd‘) order by a.oper_time desc) rank from test a ) t where t.rank=1 不存在重复数据；
select * from (select a.* ,rank() over(partition by a.task_type,to_char(a.oper_time,‘yyyymmdd‘) order by a.oper_time desc) rank from test a ) t where t.rank=1 重复数据；
row_number()over(partiton by order by ) rank() over(partition by order by )
原文：https://www.cnblogs.com/zhanglin123/p/13993889.html