Question

如果已经回答道歉，我搜索并搜索但找不到这个确切的场景。

我有一个用户表和一个包含活动的表（添加或删除）。我想通过查询将这些结合到一个结果中，将AddDate和RemoveDate作为查询中的列。

以下是我的数据示例，以及我正在寻找的内容。

Users
==============
ID  User
--------------
1   John Doe
2   Jane Doe
3   John Smith

Activities
===========================================
ID  UserID  ActivityType    ActivityDate
-------------------------------------------
1   1       Add             1/1/2017
2   2       Add             1/3/2017
3   3       Add             2/2/2017
4   1       Remove          2/6/2017

这就是我要回复的问题

User           AddDate     RemoveDate
=====================================
John Doe       1/1/2017    2/6/2017
Jane Doe       1/3/2017
John Smith     2/2/2017

Answer 1

今天早上再次看完它后，我想通了。发布答案的时候我不可避免地会忘记一年后的问题，并且必须向谷歌寻求答案！

SELECT [User], 
       [AddDate],
       [RemoveDate]
FROM (( [Users]
LEFT JOIN ( SELECT [UserID],
                   [ActivityDate] AS AddDate
            FROM   [Activities]
            WHERE  [ActivityType] = "Add" ) AS [A1]
                   ON [Users].[ID] = [A1].[UserID])
LEFT JOIN ( SELECT [UserID],
                   [ActivityDate] AS RemoveDate
            FROM   [Activities]
            WHERE  [ActivityType] = "Remove" ) AS [A2]
                   ON [Users].[ID] = [A2].[UserID])

构建查询以在单行上为同一用户连接多个行（Access 2010）

1 个答案: