分組，計數和在哪裏

Question

我很難過，抓撓我的頭。它一定很簡單，但我沒有看到它。

比方說，我有四個表：

video = id 
hastag = id, tag_id, video_id 
hasteam = id, team_id, video_id 
hasidol = id, idol_id, video_id 

此數據集（只是爲例）：

video = (1), (2), (3) 
hastag = (1, 1, 1), (2, 1, 2), (3, 2, 3) 
hasteam = (1, 1, 1), (2, 1, 3), (3, 2, 2) 
hasidol = (1, 1, 3) 

而這個查詢：

SELECT v.id , 
COUNT(vhtag.id), 
COUNT(vhteam.id), 
COUNT(vhidol.id) 
FROM video v 
LEFT JOIN hastag vhtag ON vhtag.video_id = v.id 
LEFT JOIN hasteam vhteam ON vhteam.video_id = v.id 
LEFT JOIN hasidol vhidol ON vhidol.video_id = v.id 

WHERE 
v.id <> 1 
AND 
(
    vhtag.tag_id IN (SELECT htt2.tag_id FROM hastag htt2 WHERE video_id = 1) 
    OR 
    vhteam.team_id IN (SELECT htt3.team_id FROM hasteam htt3 WHERE video_id = 1) 
    OR 
    vhidol.idol_id IN (SELECT htt4.idol_id FROM hasidol htt4 WHERE video_id = 1) 
) 
GROUP BY v.id 

它給我的罪名「有」行不符合WHERE子句。例如，如果視頻行只有一個視頻標識爲1的單個團隊和一個完全不相關的標籤，那麼當它應該顯示「公共標籤時，它會給我」常用標籤數：1，常用團隊數：1「計數：0（因爲它是一個不相關的標籤），常用團隊數：1「。

現在，只要我限制查詢到只有一個「有」表，像這樣：

SELECT v.id , 
COUNT(vhtag.id) 
FROM video v 
LEFT JOIN hastag vhtag ON vhtag.video_id = v.id 

WHERE 
v.id <> 1 
AND 
(
    vhtag.tag_id IN (SELECT htt2.tag_id FROM hastag htt2 WHERE video_id = 1) 
) 
GROUP BY v.id 

然後它的工作，但問題是，當我試圖把一個以上的「有「表進入查詢。我嘗試過使用HAVING，但它不能識別「vhtag.tag_id」列。 我很明顯在這裏做錯了什麼，任何人都可以幫助我？

編輯：

這種作品：

LEFT JOIN hastag vhtag ON vhtag.video_id = v.id AND vhtag.tag_id IN (SELECT htt2.tag_id FROM hastag htt2 WHERE video_id = 1) 
LEFT JOIN hasteam vhteam ON vhteam.video_id = v.id AND vhteam.team_id IN (SELECT htt3.team_id FROM hasteam htt3 WHERE video_id = 1) 
LEFT JOIN hasidol vhidol ON vhidol.video_id = v.id AND vhidol.idol_id IN (SELECT htt4.idol_id FROM hasidol htt4 WHERE video_id = 1) 

我可以使用，在學說太（我是啞巴，忘了關於使用）。這是最佳的方式嗎？

Answer 1

儘量簡化查詢，例如以這種方式 -

SELECT 
    v.id, 
    COUNT(vhtag.id), 
    COUNT(vhteam.id), 
    COUNT(vhidol.id) 
FROM 
    video v 
LEFT JOIN (SELECT * FROM hastag WHERE video_id = 1) vhtag 
    ON vhtag.video_id = v.id 
LEFT JOIN (SELECT * FROM hasteam WHERE video_id = 1) vhteam 
    ON vhteam.video_id = v.id 
LEFT JOIN (SELECT * FROM hasidol WHERE video_id = 1) vhidol 
    ON vhidol.video_id = v.id 
WHERE 
    v.id <> 1 
GROUP BY 
    v.id 

它是否給正確的結果？

輸出：

+------+-----------------+------------------+------------------+ 
| id | COUNT(vhtag.id) | COUNT(vhteam.id) | COUNT(vhidol.id) | 
+------+-----------------+------------------+------------------+ 
| 2 |    0 |    0 |    0 | 
| 3 |    0 |    0 |    0 | 
+------+-----------------+------------------+------------------+ 

Answer 2

您有您的聯接是使每個團隊內部的交叉連接的問題。

最簡單的方法是做計數不同：

SELECT v.id , COUNT(distinct vhtag.id), COUNT(distinct vhteam.id), 
     COUNT(distinct vhidol.id) 
FROM video v LEFT JOIN 
    hastag vhtag 
    ON vhtag.video_id = v.id 
    LEFT JOIN hasteam vhteam 
    ON vhteam.video_id = v.id 
    LEFT JOIN hasidol vhidol 
    ON vhidol.video_id = v.id 

真正的解決方案是聚合的每個值分別，然後將結果結合在一起。