SQL Server：按用戶和日期計算分組

Question

在我的SQL Server 2008中，我得到了一個表，其中存儲了每個用戶的操作的datetime。它看起來像這樣：

id | username | action | actionDate 
------------------------------------ 
1 | bob  | add  | 2015-08-15 11:20:12 
2 | bob  | add  | 2015-08-15 11:21:52 
3 | sandra  | add  | 2015-08-15 11:25:32 
4 | sandra  | add  | 2015-08-15 11:26:32 
5 | bob  | add  | 2015-08-15 11:31:52 
6 | sandra  | add  | 2015-08-16 13:46:32 
7 | sandra  | add  | 2015-08-16 13:26:32 
8 | bob  | add  | 2015-08-16 13:31:52 
9 | sandra  | add  | 2015-08-16 13:46:32 

這張表比較大，並且存儲了很多天的數據。所以我需要知道每個用戶每天做多少次「添加」操作。例如： -

actionDate | username | countRow 
2015-08-15 | bob  | 3 
2015-08-15 | sandra  | 2 
2015-08-16 | bob  | 2 
2015-08-16 | sandra  | 3 

我已經嘗試了很多不同的查詢，但我仍然不能得到它。我認爲最接近的查詢是這樣的：

SELECT S.username, S.actionDate, C.countRow 
    From dbo.actionTable S 
    INNER JOIN(SELECT Convert(date, actionDate),count(username) as countRow 
       FROM dbo.actionTable 
       WHERE action = 'add' 
       GROUP BY Convert(date, actionDate)) C ON S.actionDate = C.actionDate 

但這個查詢返回的錯誤數據太多了。請告訴我我錯在哪裏。

Answer 1

爲什麼不直接做..

select 
    username 
    ,convert(date,actionDate) as actionDate 
    ,count(*) as countRow 
from actionTable 
where action = 'add' 
group by username 
     ,convert(date,actionDate) 

Answer 2

嘗試

select convert(date,actionDate) actionDate, username, 
count(*) coutntRow from actionTable 
where action = 'add' 
group by convert(date,actionDate), userName 

Answer 3

SELECT S.username, Convert(date, S.actionDate), count(S.id) as countRow,S.action 
From dbo.actionTable S WHERE S.action = 'add' 
GROUP BY Convert(date, S.actionDate),S.action,S.username 

Answer 4

I recommend you the normalization of your database. 

If I were you I do this: 
++++++++++++++++++++++++ 
Table name: **userTable** 
------------------------------------ 
id | username 
------------------------------------ 
1 | bob   
2 | sandra 
3 | peter 
++++++++++++++++++++++++ 
Table name: **actionTable** 
------------------------------------ 
id | action 
------------------------------------ 
1 | add 
2 | update 
3 | delete 
++++++++++++++++++++++++ 
Table name: **actionUser** 
------------------------------------ 
ID | user_id | action_id | actionDate 
------------------------------------ 
| 1 | 1  | 1  | 2015-08-15 11:20:12 
| 2 | 2  | 2  | 2015-08-15 11:21:52 
| 3 | 1  | 1  | 2015-08-15 11:25:32 

這是此問題的一個更好的架構。

和查詢應該是這樣的：

SELECT COUNT(user_id) 
FROM dbo.actionUser 
WHERE user_id = % 

其中％是用戶的ID。