LEFT JOIN订单和限制

Question

这是我的查询:

SELECT `p`.`name` AS 'postauthor', `a`.`name` AS 'authorname',
       `fr`.`pid`, `fp`.`post_topic` AS 'threadname', `fr`.`reason`
  FROM `z_forum_reports` `fr`
  LEFT JOIN `forums` `f` ON (`f`.`id` = `fr`.`pid`)
  LEFT JOIN `forums` `fp` ON (`f`.`first_post` = `fp`.`id`) 
  LEFT JOIN `ps` `p` ON (`p`.`id` = `f`.`author_guid`)
  LEFT JOIN `ps` `a` ON (`a`.`account_id` = `fr`.`author`)

我的问题是这个左连接:

SELECT `a`.`name`, `a`.`level`
[..]
LEFT JOIN `ps` `a` ON (`a`.`account_id` = `fr`.`author`)

因为,如果a有很多行,它会像我的情况一样返回:

NAME  | LEVEL
Test1 | 1
Test2 | 120
Test3 | 2
Test4 | 1 

我希望它选择a.name与order水平desc和限制1,所以它会更高回报的名字level在那里(a.account_id = fr.author).

希望你能得到我.如果没有,请随时发表评论.

Answer 1

尝试更换:

LEFT JOIN ps a ON a.account_id = fr.author

有:

LEFT JOIN ps a 
  ON a.PrimaryKey                         --- the Primary Key of ps
     = ( SELECT b.PrimaryKey 
         FROM ps AS b 
         WHERE b.account_id = fr.author
         ORDER BY b.level DESC
         LIMIT 1
       )