MySQL查詢需要1天以上

Question

MySQL查詢時間超過1天，如何speet起來：

update posts set category_id = (
    SELECT keyword_id 
    FROM post_keywords 
    where keyword_id IN (
     SELECT keyword_id 
     FROM post_keywords 
     where id_post = posts.id_post) 
    group by keyword_id 
    order by count(keyword_id) DESC 
    limit 0,1 
); 

任何解決方案？

Answer 1

這不完全是一回事，但結果仍然是你想要的那樣。我主要好奇如何（IF !?）這可能會影響性能。

UPDATE posts 
    SET category_id = (
         SELECT pkw.keyword_id 
          FROM post_keywords pkw 
          JOIN (
            SELECT keyword_id, cnt = COUNT(*) 
             FROM post_keywords 
            GROUP BY keyword_id) cnts 
          ON cnts.keyword_id = pkw.keyword_id 
         WHERE pkw.id_post = posts.id_post 
         ORDER BY cnt DESC 
         LIMIT 0,1 

        )