Question

我在带有日期戳的表中记录了用户操作。

每次用户进入项目时，都会记录他们查看该项目并标记日期时间。

我想获得用户最后进入的前20个项目。

这是我到目前为止所做的：

SELECT DISTINCT TOP (20) Users_Tran_ID
FROM App_UserLog
WHERE (Users_ID = 'ADMIN') AND (Users_Transaction LIKE 'Permit Viewed%')
ORDER BY App_UserLog.Users_LogDate DESC

问题是，我不想在输出中使用Users_LogDate，因为我需要UNIQUE Users_Tran_ID。

当我从SELECT中删除Users_LogDate时，我收到以下错误：

ORDER BY items must appear in the select list if SELECT DISTINCT is specified.

这是我得到的基本选择和结果集。我只想要不同的Users_Tran_ID而只需要TOP 20.

ADMIN   Permit Viewed   B2011-0012  2013-08-29 17:35:04.000
ADMIN   Permit Viewed   B2011-0012  2013-08-29 17:29:09.000
ADMIN   Permit Viewed   B2006-0043  2013-08-29 17:29:05.000
ADMIN   Permit Viewed   B2011-0012  2013-08-29 17:28:49.000
ADMIN   Permit Viewed   B2008-0167  2013-08-29 17:17:13.000
ADMIN   Permit Viewed   B2006-0043  2013-08-29 17:17:08.000
ADMIN   Permit Viewed   B2011-0012  2013-08-29 17:16:55.000
ADMIN   Permit Viewed   B2011-0012  2013-08-29 17:16:45.000
ADMIN   Permit Viewed   B2011-0012  2013-08-29 17:16:38.000
ADMIN   Permit Viewed   B2007-0478  2013-08-29 17:16:32.000
ADMIN   Permit Viewed   B2011-0012  2013-08-29 11:39:59.000
ADMIN   Permit Viewed   B2007-0478  2013-08-29 11:22:05.000
ADMIN   Permit Viewed   B2007-0478  2013-08-29 11:22:03.000
ADMIN   Permit Viewed   B2011-0012  2013-08-29 10:23:17.000
ADMIN   Permit Viewed   B2011-0012  2013-08-29 10:21:58.000
ADMIN   Permit Viewed   B2011-0012  2013-08-29 10:20:41.000
ADMIN   Permit Viewed   B2011-0012  2013-08-29 10:20:37.000
ADMIN   Permit Viewed   B2007-0478  2013-08-29 10:18:01.000
ADMIN   Permit Viewed   B2007-0478  2013-08-29 10:17:58.000
ADMIN   Permit Viewed   B2011-0012  2013-08-29 10:17:54.000
ADMIN   Permit Viewed   B2011-0012  2013-08-29 10:01:50.000
ADMIN   Permit Viewed   B2011-0012  2013-08-29 10:01:48.000
ADMIN   Permit Viewed   B2007-0478  2013-08-29 09:56:32.000
ADMIN   Permit Viewed   B2007-0478  2013-08-29 09:53:31.000
ADMIN   Permit Viewed   B2007-0478  2013-08-29 09:53:27.000
ADMIN   Permit Viewed   ENG2012-0141    2013-08-15 12:51:09.000
ADMIN   Permit Viewed   ENG2012-0141    2013-08-15 12:51:07.000
ADMIN   Permit Viewed   BLD2012-0094    2013-08-13 12:01:39.000
ADMIN   Permit Viewed   ENG2013-0047    2013-08-05 10:40:34.000
ADMIN   Permit Viewed   ENG2013-0047    2013-08-05 10:40:28.000
ADMIN   Permit Viewed   ENG2013-0047    2013-08-05 10:40:24.000
ADMIN   Permit Viewed   ENG2013-0047    2013-08-05 10:40:21.000
ADMIN   Permit Viewed   ENG2013-0047    2013-08-05 10:40:13.000
ADMIN   Permit Viewed   ENG2013-0047    2013-08-05 10:40:09.000
ADMIN   Permit Viewed   ENG2013-0047    2013-08-05 10:40:07.000
ADMIN   Permit Viewed   ENG2012-0141    2013-08-05 10:37:55.000
ADMIN   Permit Viewed   ENG2012-0141    2013-08-05 10:37:50.000
ADMIN   Permit Viewed   ENG2012-0141    2013-08-05 10:37:46.000
ADMIN   Permit Viewed   ENG2012-0141    2013-08-05 10:37:40.000
ADMIN   Permit Viewed   ENG2012-0141    2013-08-05 10:37:33.000
ADMIN   Permit Viewed   ENG2012-0141    2013-08-05 10:37:31.000
ADMIN   Permit Viewed   BLD2012-0919    2013-08-05 10:27:21.000
ADMIN   Permit Viewed   BLD2012-0919    2013-08-05 10:27:17.000
ADMIN   Permit Viewed   ENG2012-0119    2013-08-05 10:26:51.000
ADMIN   Permit Viewed   ENG2012-0119    2013-08-05 10:26:48.000

我该怎么做？

Answer 1

您想使用group by而不是distinct：

SELECT TOP (20) Users_Tran_ID
FROM App_UserLog
WHERE (Users_ID = 'ADMIN') AND (Users_Transaction LIKE 'Permit Viewed%')
GROUP BY Users_Tran_ID
ORDER BY max(App_UserLog.Users_LogDate) DESC;

通过聚合，您可以指定要按最新的logdate排序。瞧，那应该做你想做的事。

Answer 2

SELECT Users_ID, Users_Transaction, Users_Tran_ID
FROM (
    SELECT DISTINCT TOP (20) Users_ID, Users_Transaction, Users_Tran_ID, Users_LogDate
    FROM App_UserLog
    WHERE (Users_ID = 'ADMIN') AND (Users_Transaction LIKE 'Permit Viewed%')
    ORDER BY App_UserLog.Users_LogDate DESC
) as a

Answer 3

你在寻找这样的东西：

SELECT TOP 20 Users_ID, 
              Users_Transaction, 
              Users_Tran_ID 
         FROM ( SELECT Users_ID, 
                       Users_Transaction, 
                       Users_Tran_ID, 
                       max(Users_LogDate) as MaxUsers_LogDate
                  FROM App_UserLog
                 WHERE (Users_ID = 'ADMIN') AND 
                       (Users_Transaction LIKE 'Permit Viewed%')
              GROUP BY Users_ID, Users_Transaction, Users_Tran_ID
             ) AS TopTransactions
ORDER BY MaxUsers_LogDate DESC

请参阅SQLFIDDLE

在查询中选择TOP 20 Distinct Rows

3 个答案: