mysql - 如何向具有 GROUP BY 和 HAVING 子句的查询再添加一个连接？

Question

这是我的查询:

SELECT p.*
FROM posts p
INNER JOIN tags_pivot tp 
     ON p.id = tp.post_id
INNER JOIN tags t
     ON t.id = tp.tag_id AND t.name IN ('mysql', 'php')
GROUP BY p.id
HAVING COUNT(*) = 2;

它选择所有带有 [mysql] 和 [php] 标签的帖子。我还有一个名为 "Category" 的存在。它类似于“标签”，只是每个帖子唯一。

无论如何，我需要将其附加到上面的查询中:

INNER JOIN category_pivote cp
        ON p.id = cp.post_id
INNER JOIN categories c
        ON c.id = cp.category_id AND c.name = "technology"

如何组合这两个查询？

Answer 1

一种使用join的方法是:

SELECT p.*
FROM posts p INNER JOIN
     category_pivote cp
     ON p.id = cp.post_id INNER JOIN
     categories c
     ON c.id = cp.category_id AND c.name = 'technology' INNER JOIN
     tags_pivot tp 
     ON p.id = tp.post_id INNER JOIN
     tags t
     ON t.id = tp.tag_id AND t.name IN ('mysql', 'php')
GROUP BY p.id
HAVING COUNT(DISTINCT t.name) = 2;

我添加了 DISTINCT 以防多个类别匹配(尽管这似乎不太可能)。您还可以使用:

HAVING GROUP_CONCAT(DISTINCT t.name ORDER BY t.name) = 'mysql,php';