MYSQL连接3台

Question

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` 

如何添加另一个表给它为了得到其他的细节，其中__Temp.friend现在T3.userid是共同点

Answer 1

试试这个：

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