複雜的SQL查詢

Question

我有這些表：

 
- Users 
    - id 
- Photos 
    - id 
    - user_id 
- Classifications 
    - id 
    - user_id 
    - photo_id 

我想通過照片，他們自己的分類+的總數訂購用戶。

我寫此查詢：

 
SELECT users.id, 
COUNT(photos.id) AS n_photo, 
COUNT(classifications.id) AS n_classifications, 
(COUNT(photos.id) + COUNT(classifications.id)) AS n_sum 
FROM users 
LEFT JOIN photos ON (photos.user_id = users.id) 
LEFT JOIN classifications ON (classifications.user_id = users.id) 
GROUP BY users.id 
ORDER BY (COUNT(photos.id) + COUNT(classifications.id)) DESC 

的問題是，我希望這個查詢不起作用，並且返回高的數字，而我只有一個數據庫中的幾張照片和分類。它返回如下所示的內容：

id n_photo n_classifications n_sum 
29 19241 19241     38482 
16 16905 16905     33810 
1 431  0      431 
...

Answer 1

你錯過了不同。

SELECT U.ID, COUNT(DISTINCT P.Id)+COUNT(DISTINCT C.Id) Count 
    FROM User U 
    LEFT JOIN Photos P ON P.User_Id=U.Id 
    LEFT JOIN Classifications C ON C.User_Id=U.Id 
    GROUP BY U.Id 
    ORDER BY COUNT(DISTINCT P.Id)+COUNT(DISTINCT C.ID) 

Answer 2

我可能誤解你的模式，但不應該這樣：

LEFT JOIN classifications ON (classifications.user_id = users.id) 

是這樣的：

LEFT JOIN classifications ON (classifications.user_id = users.id) 
         AND (classifications.photo_id = photos.id) 

？

Answer 3

SELECT users1.id, users1.n_photo, users2.n_classifications 
FROM (
    SELECT users.id, COUNT(photos.id) AS n_photo 
    FROM users LEFT OUTER JOIN photos ON photos.user_id = users.id 
    GROUP BY users.id 
) users1 
    INNER JOIN (
    SELECT users.id, COUNT(classifications.id) AS n_classifications 
    FROM users LEFT OUTER JOIN classifications ON classifications.user_id = users.id 
    GROUP BY users.id 
) users2 ON users1.id = users1.id 

Answer 4

嘗試一些更喜歡這個：

SELECT users.id as n_id, 
(SELECT COUNT(photos.id) FROM photos WHERE photos.user_id = n_id) AS n_photos, 
(SELECT COUNT(classifications,id) FROM classifications WHERE classifications.user_id = n_id) AS n_classifications, 
(n_photos + n_classifications) AS n_sum 
FROM users 
GROUP BY n_id 
ORDER BY n_sum DESC