Question

感谢您对我的糟糕问题的反馈。第一次在这里。

我正在Visual Studio中使用SQlite和C＃。

这是我表中数据的示例：

TABLE: VIDEOS
-------------
ID  VideoName             VideoStarID       VideoCostarID
--------------------------------------------------------------
1   Casablanca                23                 43
2   Maltese Falcon            23                156
3   Matrix                   234                312
4   Matrix Reloaded          234                312
5   Matrix Revolutions       234                312
6   Pompeii                  312

TABLE: STARS
-------------
ID  StarName        
------------------------------
23  Humphrey Bogart 
43  Ingrid Bergman
156 Mary Astor
234 Keanu Reeves
312 Carrie-Anne Moss

TABLE: TAGS
-------------
ID  TagName     
------------------------------
1   Action
2   Classic
3   Drama
4   Horror
5   Thriller
6   Sci-Fi
7   Romance
8   Western
9   War
10  Film Noir
11  Comedy
12  History
13  Dystopia

TABLE: VIDEO_TAGS
-------------
VideoID     TagID   
------------------------------
1            2
1            5
1            7
1            9
2            1
2            2
2            5
3            1
3            5
3            6
3            13
4            1
4            5
4            6
4            13
5            1
5            5
5            6
5            13
6            12
6            3

我想选择所有由Carrie-Anne Moss和Keanu Reeves主演的，带有“动作”，“科幻”和“惊悚”标签的电影。实际上，我的查询将比将来的查询更为复杂，因为我将必须能够包括年份，工作室，奥斯卡提名，获胜奖，评级等参数；但目前，我遇到的问题是我无法获得如下输出：

-----------------------------------------------------------------------------------------------------
|VideoID |      VideoName    |   StarName   |    CostarName    |         Tags                       |
-----------------------------------------------------------------------------------------------------
|   3    |Matrix             | Keanu Reeves | Carrie-Anne Moss | Action, Sci-Fi, Thriller, Dystopia |
|   4    |Matrix Reloaded    | Keanu Reeves | Carrie-Anne Moss | Action, Sci-Fi, Thriller, Dystopia |
|   4    |Matrix Revolutions | Keanu Reeves | Carrie-Anne Moss | Action, Sci-Fi, Thriller, Dystopia |
-----------------------------------------------------------------------------------------------------

我尝试了这个（显然）错误的查询：

SELECT VIDEOS.ID, VIDEOS.VideoName, VIDEOS.StarID, VIDEOS.CostarID, STARS.StarName, GROUP_CONCAT(TAGS.Name) AS Tags
FROM VIDEOS
INNER JOIN STARS ON VIDEOS.StarID = STARS.ID
INNER JOIN VIDEO_TAGS ON VIDEOS.ID = VIDEO_TAGS.VideoID
INNER JOIN TAGS ON TAGS.ID = VIDEO_TAGS.TagID
WHERE 
VIDEOS.StarID = 234 AND 
VIDEOS.CostarID = 312 AND
VIDEO_TAGS = 1 AND
VIDEO_TAGS = 5 AND
VIDEO_TAGS = 6

结果仅一行。它不能获取所有电影。我也没有得到想要的标签。

希望此信息有所帮助。任何帮助将不胜感激。

谢谢。

Answer 1

您缺少的是此子查询：

  select distinct vt.videoid from video_tags vt
  where (select count(distinct tagid) from video_tags where videoid = vt.videoid and tagid in (1, 5, 6)) = 3

为您提供包含所有3个标签的视频的ID。

所以用这个：

select v.id VideoID, v.videoname VideoName, s1.starname StarName, s2.starname CoStarName,
  (select group_concat(tagname) from tags where id in (select tagid from video_tags where  videoid = v.id)) Tags 
from videos v inner join (
  select distinct vt.videoid from video_tags vt
  where (select count(distinct tagid) from video_tags where videoid = vt.videoid and tagid in (1, 5, 6)) = 3
) f
on f.videoid = v.id
inner join stars s1
on s1.id = v.videostarid
left join stars s2
on s2.id = v.videocostarid
where s1.id = 234 and s2.id = 312

请参见demo

Answer 2

由于缺少GROUP BY，因此只得到1行。另外，您需要将IN用于3个标签。

SELECT VIDEOS.ID, VIDEOS.VideoName, VIDEOS.StarID, VIDEOS.CostarID, STARS.StarName, GROUP_CONCAT(TAGS.TagName) AS Tags
FROM VIDEOS
INNER JOIN STARS ON VIDEOS.StarID = STARS.ID
INNER JOIN VIDEO_TAGS ON VIDEOS.ID = VIDEO_TAGS.VideoID
INNER JOIN TAGS ON TAGS.ID = VIDEO_TAGS.TagID
WHERE 
VIDEOS.StarID = 234 AND 
VIDEOS.CostarID = 312 AND
VIDEO_TAGS.TagID IN (1,5,6)
GROUP BY VIDEOS.ID

DBFiddle here

选择带有多个标签的项目，然后从其他表格中选择详细信息

2 个答案: