mysql - 简单的最大功能困扰着我

Question

简单的查询困扰着我。我似乎做错了，但我知道这很简单:

Select username
From hsi.wftransactionlog
where logdate = (Select max(logdate) From hsi.wftransactionlog) 

我想返回具有最高日志日期的用户名。

我正在为每个用户名查找 1 行。日期最长的那个。

Answer 1

I am looking for 1 row per username. The one with the max date.

那么你可能想做一个group by，比如

Select t1.*
From hsi.wftransactionlog t1
join (Select username, max(logdate) as maxlogdate
From hsi.wftransactionlog
group by username) xxx 
on t1.username = xxx.username and t1.logdate = xxx.maxlogdate;