帮助优化子查询

Question

此查询获取与其他新闻文章类似标记的新闻文章。我是否可以消除这些我没有看到的子查询之一？

SELECT id, 
       title, 
       comment_count
  FROM NEWS
 WHERE (franchise_id = 1 OR franchise_id = 0)
   AND draft = 0
   AND id != 459
   AND id IN (SELECT news_id
                FROM news_tag_association
               WHERE tag_id IN (SELECT tag_id
                                  FROM news_tag_association
                                 WHERE news_id = 459))                               
 LIMIT 0, 5;

Answer 1

是的，没有 GROUP BY 或类似的，所以你可以使用普通的自连接：

SELECT
    id, title, comment_count
FROM news
JOIN news_tag_association n2t1 ON (news.id = n2t1.news_id)
JOIN news_tag_association n2t2 ON (n2t1.tag_id = n2t2.tag_id)
WHERE franchise_id IN (0, 1)
    AND draft = 0
    AND id != 459
    AND n2t2.news_id = 459
LIMIT 0,5;