分组，计数和在哪里

Question

我很难过，抓挠我的头。它一定很简单，但我没有看到它。

比方说，我有四个表：

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

此数据集（只是为例）：

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) 

而这个查询：

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 

它给我的罪名“有”行不符合WHERE子句。例如，如果视频行只有一个视频标识为1的单个团队和一个完全不相关的标签，那么当它应该显示“公共标签时，它会给我”常用标签数：1，常用团队数：1“计数：0（因为它是一个不相关的标签），常用团队数：1“。

现在，只要我限制查询到只有一个“有”表，像这样：

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 

然后它的工作，但问题是，当我试图把一个以上的“有“表进入查询。我尝试过使用HAVING，但它不能识别“vhtag.tag_id”列。 我很明显在这里做错了什么，任何人都可以帮助我？

编辑：

这种作品：

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，在学说太（我是哑巴，忘了关于使用）。这是最佳的方式吗？

Answer 1

尽量简化查询，例如以这种方式 -

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 

它是否给正确的结果？

输出：

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

Answer 2

您有您的联接是使每个团队内部的交叉连接的问题。

最简单的方法是做计数不同：

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 

真正的解决方案是聚合的每个值分别，然后将结果结合在一起。