Question

原始帖子标题： 查询从字段中删除重复值关于表格列中最大值的存在保持最近的

我有一个名为Idle_info的表：列是

open_date(date/time),time_from(date/time),duration(number),user(text)

如果open_date和time_from相同，我想删除这些值。只有在持续时间最长的情况下才会保存该值。

我试过了：

DELETE FROM Idle_info 
WHERE idle_duration NOT IN (SELECT MAX(i.idle_duration) 
FROM Idle_info i 
WHERE i.open_date = open_date AND i.time_from=time_from AND i.user=user 
GROUP BY i.open_date,i.time_from,i.idle_duration,i.user

但没有工作

感谢

Answer 1

这是您的查询：

DELETE FROM Idle_info
     WHERE idle_duration NOT IN (SELECT MAX(i.idle_duration)
                                 FROM Idle_info i
                                 WHERE i.open_date = open_date AND i.time_from = time_from AND
                                       i.user = user
                                 GROUP BY i.open_date,i.time_from, i.idle_duration, i.user
                                )

我的猜测是，您希望保留一组给定条件的最新记录。你有两个问题。一个是缺乏相关性。第二个是group by子句。我相信以下是你想要的：

DELETE FROM Idle_info i
     WHERE i.idle_duration < (SELECT MAX(i.idle_duration)
                              FROM Idle_info i2
                              WHERE i.open_date = i2.open_date AND
                                    i.time_from = i2.time_from AND
                                    i.user = i2.user
                             );

Answer 2

试试这个：

DELETE FROM Idle_info r1
WHERE exists (select 1 
                  from idle_info r2 
                  where r1.user=r2.user 
                    and r1.time_from=r2.time_from 
                    and r1.open_date=r2.open_date
                    and r1.idle_duration<r2.idle_duration
              )

删除重复项，保留最新记录

2 个答案: