Question

考虑我有三张桌子：

电影（电影1，电影2等）
类别（动作，悬疑等）
Movies_Categories（电影1 - ＆gt;动作，电影1 - ＆gt;悬疑，电影2 - ＆gt;悬疑等）

如何仅使用1个查询选择仅属于或不属于特定类别的电影？

谢谢！

Answer 1

所属：

    SELECT m.*
      FROM movies m
INNER JOIN movies_categories mc
        ON m.id = mc.movie_id
INNER JOIN categories c
        ON c.id = mc.category_id
       AND c.name = 'action';

不属于：

         SELECT m.*
           FROM movies m
LEFT OUTER JOIN (SELECT mc.movie_id
                   FROM movies_categories mc
             INNER JOIN categories c
                     ON c.id = mc.category_id
                    AND c.name = 'action') mcx
             ON m.id = mcx.movie_id
          WHERE mcx.movie_id IS NULL

Answer 2

    SELECT m.*,
           IF(mc.movie_id IS NULL, 'doesnt belong', 'belongs')
      FROM Movies m
 LEFT JOIN Movies_Categories mc ON mc.movie_id = m.id
                               AND mc.category_id = (SELECT id
                                                       FROM categories
                                                      WHERE name = 'action')

帮助（有点简单）MySQL JOIN

2 个答案: