构建查询以在单行上为同一用户连接多行 (Access 2010)

Question

很抱歉，如果这个问题已经得到解答，我搜索了又搜索，但找不到这个确切的场景。

我有 table 个用户，table 个有活动（添加或删除）。我想通过查询将这些组合成一个结果，并将 AddDate 和 RemoveDate 作为查询中的列。

这是我的数据示例，也是我要查找的内容。

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

这就是我想要查询的 return

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

Answer 1

今早又新鲜看了一遍，明白了。当我不可避免地忘记一年后的答案并且不得不 Google 寻找答案时发布答案！

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行 (Access 2010)

Build a query to join multiple rows for same user on a single row (Access 2010)

ms-access-2010