查询数据中的第一条和最后一条

方法一：

select * from s600520 a
where not exists
(select 1 from s600520 b where a.CJDate =b.CJDate and b.CJTime >a.CJTime )
order by CJDate

方法二：
select * from (select *,row_number() over(partition by CJDate order by CJTime desc) rid from s600520)as l where rid =1