我有一个
PHP板的多个表.
我需要一个有效的查询,与发布的用户选择所有类别,所有主题,主题的最后发布.使用我的查询运行它需要5-8秒.
我使用last_post_id字段对主题表进行了优化,但我需要一个更好的解决方案.
结构体
forum_categories ~ 15 lines id|name|... forum_topics ~ 150 lines id|name|category_id|... forum_posts ~ 1.000.000 lines id|body|topic_id|user_id|... users ~ 30.000 lines id|username|... category 1 - topic 1 - last post1 | user1 - topic 2 - last post2 | user2 ... category 2 - topic 3 - last post3 | user3 ... ...
最后查询(这是我朋友的帮助.但这也很慢.)
SELECT c.NAME AS category,t.NAME AS topic,p.body AS post,p.username AS username FROM forum_categories AS c JOIN forum_topics AS t ON t.category_id = c.id JOIN (SELECT * FROM (SELECT p.body,p.topic_id,u.username FROM forum_posts AS p JOIN users AS u ON u.id = p.user_id ORDER BY p.id DESC) AS t GROUP BY topic_id) AS p ON t.id = p.topic_id
Exaplain查询
查询统计
标题是:排序,状态,时间|状态,所有时间,pct.时间,电话,时间
解决方法
我认为“主题的最后一篇文章”是您查询的关键点.这就是你在大多数内部查询中使用ORDER BY的原因,但这会产生两个子查询.
更新后的版本
CREATE TEMPORARY TABLE last_post_per_topic_t ENGINE = MEMORY SELECT topic_id,MAX(id) AS id -----+ FROM forum_posts --> find last post id per topic GROUP BY topic_id; -----------------+ ALTER TABLE last_post_per_topic_t ADD INDEX (id,topic_id); SELECT * FROM forum_categories AS c INNER JOIN forum_topics t ON c.id = t.category_id INNER JOIN forum_posts p ON p.topic_id = t.id INNER JOIN last_post_per_topic_t ON last_post_per_topic_t.topic_id = t.id AND last_post_per_topic_t.id = p.id; INNER JOIN users u ON p.user_id = u.id;
第一版
SELECT * FROM forum_categories AS c INNER JOIN forum_topics t ON c.id = t.category_id INNER JOIN forum_posts p ON p.topic_id = t.id INNER JOIN ( SELECT topic_id,MAX(id) AS id -----+ FROM forum_posts --- find last post_id per topic GROUP BY topic_id ---------------+ ) last_post_per_topic_t ON last_post_per_topic_t.topic_id = t.id AND last_post_per_topic_t.id = p.id;