Question

此查询工作正常，但使用3.3493执行，请帮我查看是否有办法更好地优化它。

SELECT u.ID, 
(SELECT meta_value FROM wpcg_usermeta WHERE meta_key = 'first_name' AND user_id = u.ID ) AS firstname, 
(SELECT meta_value FROM wpcg_usermeta WHERE meta_key = 'last_name' AND user_id = u.ID ) AS lastname, 
(SELECT meta_value FROM wpcg_usermeta WHERE meta_key = 'user_avatar_thumb' AND user_id = u.ID ) AS avatarurl, 
(SELECT COUNT(m.user_id) FROM wpcg_usermeta AS m , wpcg_users AS uz  WHERE m.user_id = uz.ID AND m.meta_key = 'user_parent' AND m.meta_value = u.ID AND u.user_registered BETWEEN DATE_SUB(NOW(), INTERVAL 7 DAY) AND NOW()) AS referral_users 
FROM wpcg_users AS u 
WHERE (SELECT COUNT( user_id ) FROM wpcg_usermeta WHERE meta_key = 'user_parent' AND meta_value = u.ID ) > 0 
ORDER BY referral_users DESC LIMIT 15 OFFSET 0

Answer 1

考虑重组您的查询

Select col1, col2, col3, ...

FROM wpcg_users AS u 
JOIN wpcg_usermeta m on u.ID = m.user_id
where meta_key in ('first_name', 'last_name', ...)

您可以通过重新构建查询来消除许多子查询，从而提高性能。如果在select中有这样的子查询，则会为每一行运行。

Answer 2

首先，提供使用过的表的元数据库和数据库的类型 - 列，索引，表的类型等（它看起来像MySql，但它可能是假的）。尝试在一些简单的请求上拆分此请求。然后尝试获取有关每个请求的统计信息。还尝试减少对某些表的调用，执行嵌套的sql-c。对不起我的英语不好。我现在正在研究它）

从3.349s减少sql查询执行时间

2 个答案: