mysql - 如何从一个表中选择行并按另一个表中的列的总和对其进行排序？

Question

在 MySQL 中，我有两个表。首先是成员(member)。其次是成员(member)经验。 member_experience 表包含成员(member)获得的所有 XP 的值以及他们获得这些 XP 的原因。我想编写一个查询来选择成员并按他们的 XP 总数对结果进行排序。我编写的查询不会返回任何结果。

CREATE TABLE IF NOT EXISTS `members` (  `member_id` int(15) NOT NULL AUTO_INCREMENT,  `group_id` int(15) NOT NULL,  `display_name` text NOT NULL,  `email_address` text NOT NULL,  `password` text NOT NULL,  `status` tinyint(1) NOT NULL,  `activation_code` varchar(16) NOT NULL,  `date_joined` text NOT NULL  PRIMARY KEY (`member_id`)) ENGINE=InnoDB  DEFAULT CHARSET=latin1;CREATE TABLE IF NOT EXISTS `member_experience` (  `experience_id` int(15) NOT NULL AUTO_INCREMENT,  `member_id` int(15) NOT NULL,  `value` mediumint(6) NOT NULL,  `description` text NOT NULL,  `date_earned` timestamp NOT NULL DEFAULT '0000-00-00 00:00:00',  PRIMARY KEY (`experience_id`)) ENGINE=InnoDB  DEFAULT CHARSET=latin1;

这是我当前的查询:

       SELECT          m.member_id,          xp.member_id, SUM(xp.value) AS total_xp       FROM members AS m       LEFT JOIN member_experience AS xp ON (xp.member_id = m.member_id)       ORDER BY total_xp";

Answer 1

这将完成这些事情:

SELECT
  members.member_id,
  total_xp.sum_xp
FROM
  members
   LEFT JOIN
     (SELECT 
       member_id, 
       SUM(value) AS sum_xp 
     FROM 
       member_experience 
     GROUP BY 
       member_id) AS total_xp
     ON members.member_id = total_xp.member_id
ORDER BY
  total_xp.sum_xp