Question

嗨，我希望你是好人
我想根据电影类别选择类似的电影
所以我的数据库中有这个表

table movies :id,title,......,date
table movie_categories : id,id_movie,id_category
table categories : id,category

其中的类别很简单：动作，戏剧，.....
我在SQL查询中还是个小白痴，所以我希望有人可以帮助我
到目前为止，我已经尝试过了

SELECT m.*,COUNT(mc.*) AS cat_frequency 
FROM movies m,movie_categories mc 
WHERE mc.id_category IN (SELECT c.id_category FROM movie_categories c WHERE id_movie = 1)
ORDER BY cat_frequency

其中1是用户当前正在观看的电影的ID

预期结果是所有电影数据，并且类别匹配频率
例如，假设当前观看的电影具有以下类别：动作，奇幻，戏剧
因此，具有相同类别（100％：具有相同类别）的电影将按顺序排列，然后是具有相同类别（66.66％：只有2个类别被匹配）的电影，依此类推....

注意：我可以用php来做，但是我想用sql来做

Answer 1

首先，您需要了解当前的电影类别

 SELECT c.id_category 
 FROM movie_categories c 
 WHERE id_movie = 1

然后您需要检查每部电影匹配多少个类别

SELECT m.id, COUNT(*) AS cat_frequency 
FROM movies m
JOIN movie_categories mc ON m.id = mc.id_movie   
WHERE mc.id_category IN ( SELECT c.id_category 
                          FROM movie_categories c 
                          WHERE c.id_movie = 1 )
GROUP BY m.id

现在您拥有与cat匹配的数量，您将两者都加入以按该属性进行排序

SELECT m.*
FROM movies m
JOIN (
        SELECT m.id, COUNT(*) AS cat_frequency 
        FROM movies m
        JOIN movie_categories mc ON m.id = mc.id_movie    
        WHERE mc.id_category IN ( SELECT c.id_category 
                                  FROM movie_categories c 
                                  WHERE c.id_movie = 1 )
        GROUP BY m.id
     ) f
  ON m.id = f.movie_id
WHERE m.id <> 1 -- you probably dont want show the current movie.
ORDER BY f.cat_frequency DESC

Answer 2

我想您需要这样的查询：

SELECT m.title, c.id_category,COUNT(*) AS cat_frequency 
  FROM movies m
  JOIN movie_categories mc ON m.id = mc.id_movie
  JOIN categories c ON c.id_category = mc.id_category
 GROUP BY c.id_category
 ORDER BY cat_frequency DESC;

sql根据类别匹配频率选择类似的电影

2 个答案: