SQL查询从3个表中选择多对多

Question

我有3张桌子：

桌post ：

post_id    |    title
---------------------------------
      1       |   post number 1
      2       |   post number 2
      3       |   post number 3

表categories ：

category_id   |   cate_name
--------------------------------
        1        |     video
        2        |     review
        3        |     gameplay

表post_categories ：

post_id   |   category_id
---------------------------------
   1       |      1
   2       |      2
   3       |      3
   2       |      1
   3       |      2
   1       |      3

如何选择post's title和category's name ？ 结果应如下所示：

title       |   cate_name
-----------------------------------------
   post number 1    |   video, gameplay 
   post number 2    |   video, review
   post number 3    |   review, gameplay

这可能吗？

Answer 1

好的，尝试一下。

SELECT DISTINCT
  post.title as title,
  GROUP_CONCAT(categories.cate_name) as cate_name
  FROM post
    LEFT JOIN post_categories
        ON post_categories.post_id = post.post_id
    LEFT JOIN categories
        ON post_categories.category_id = categories.category_id
  GROUP BY post.post_id;

Answer 2

请尝试以下sql查询。然后您将获得完整的行。

select post.title,GROUP_CONCAT(categories.cate_name SEPARATOR ', ') from  post_categories join post ON post.post_id=post_categories.post_id join categories ON categories.category_id=post_categories.category_id group by post.title