Mysql Join:获取每个条目以及每行的总收藏夹 [英] Mysql Join:get total favourites for each item along with each row

问题描述

我的DB

1)cushbu_users

1)cushbu_users

id first_name last_name email 
   1   sh        s         [e-mail]
   2   sb        s         [e-mail]   

2)cushbu_art

2)cushbu_art

   id user_id title   image_name 
   1    1     cool    cool.jpeg
   2    2     funny   funny.jpeg   
   3    1     blaaa   blaa.jpeg
   4    2     foo     foo.jpeg

3)cushbu_mark_user_favorites-存储收藏项的详细信息

3)cushbu_mark_user_favorites-Store the details of favourited item

 id user_id art_id
  1   1       1
  2   1       2
  3   2       1
  4   2       2 

 As you see two users Favorited  two arts so the total count 
 for favourite of each art is `two`

我希望获得每位用户最喜欢的艺术品，并且总喜欢它

I want to get the favourited arts of each user with total favourite

我为id = 1的用户提供的例外输出

My excepted output for user of id=1

art_id artist_name total_fav
1       sh s        2
2       sb s        2

这是对此的查询

    SELECT
        cushbu_art.id AS art_id,
        cushbu_art.title,
        cushbu_art.image_name,
        CONCAT(
            cushbu_users.first_name,
            ' ',
            cushbu_users.last_name
        ) AS artist_name , count(cushbu_mark_user_favorites.id)  as total_fav
    FROM
        cushbu_mark_user_favorites 
    LEFT JOIN cushbu_art ON cushbu_art.id=cushbu_mark_user_favorites.art_id
    LEFT JOIN cushbu_users ON cushbu_users.id = cushbu_art.artist_id
    WHERE cushbu_mark_user_favorites.user_id=1
    GROUP BY cushbu_art.id

但是它返回

art_id artist_name total_fav
    1       sh s        1
    2       sb s        1

每行仅返回total_fav 1，但排除输出2

returns total_fav only 1 for each row but the excepted output 2

推荐答案

问题是您正在过滤WHERE cushbu_mark_user_favorites.user_id=1，因此无法从其他用户那里获得收藏夹数.这个想法是第二次加入该表，但是没有这个矛盾. 推测，未经测试...

The problem is that you are filtering WHERE cushbu_mark_user_favorites.user_id=1 so it's not possible to get the number of favorites from other users. The idea is to join the table a second time, but without this contraints. Speculating, untested...

SELECT
    cushbu_art.id AS art_id,
    cushbu_art.title,
    cushbu_art.image_name,
    CONCAT(
        cushbu_users.first_name,
        ' ',
        cushbu_users.last_name
    ) AS artist_name , b.favorites_count as total_fav
FROM
    cushbu_mark_user_favorites 
LEFT JOIN cushbu_art ON cushbu_art.id=cushbu_mark_user_favorites.art_id
LEFT JOIN cushbu_users ON cushbu_users.id = cushbu_art.artist_id
LEFT JOIN (SELECT art_id,count(*) as favorites_count FROM cushbu_mark_user_favorites GROUP BY art_id) as b ON b.art_id=cushbu_art.id
WHERE cushbu_mark_user_favorites.user_id=1
GROUP BY cushbu_art.id

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