MYSQL连接第三个表

我有以下MYSQL

SELECT T2.name as username, T2.id as userid, 
       T2.lastactivity as lastactivity, T2.photo as avatar
FROM exchange AS T2
  INNER JOIN 
    ( SELECT (CASE WHEN `buddy`.`penpalA` = 887 
                     THEN `buddy`.`penpalB` 
                     ELSE `buddy`.`penpalA` 
              END) AS 'friend'
      FROM `buddy`
      WHERE status = 1 AND `penpalA` = 887
         OR `penpalB` = 887
    ) AS _Temp 
    ON _Temp.friend = T2.`id`

如何向其中添加另一个表以获取其他详细信息，其中uu Temp.friend和now T3.userid是共同的分母

请尝试以下方法：

   SELECT T2.name as username, T2.id as userid, 
           T2.lastactivity as lastactivity, T2.photo as avatar,T3.*
    FROM exchange AS T2
      INNER JOIN 
        ( SELECT (CASE WHEN `buddy`.`penpalA` = 887 
                         THEN `buddy`.`penpalB` 
                         ELSE `buddy`.`penpalA` 
                  END) AS 'friend'
          FROM `buddy`
          WHERE status = 1 AND `penpalA` = 887
             OR `penpalB` = 887
        ) AS _Temp 
        ON _Temp.friend = T2.`id`
     LEFT JOIN details T3 ON _Temp.friend=T3.UserId

---

祝贺所有这些都有问题吗？@JakeStainer那么你的问题是什么？我如何向联接中添加另一个表，并从另一个与用户ID链接的表中获取详细信息（不相关）：我认为

where

可能需要括号：

status=1和（penpalA=887或penpalB=887）

hi，我只在T3中实际存在用户ID的地方得到结果，我需要它，这样如果T3中没有任何内容，那么它只会显示blanksI将最终连接更改为左连接，这应该满足您的需要。。。