SQL查詢GROUP BY ID過濾器？

Question

這是查詢的輸出：

 
SELECT * FROM 
        ((SELECT 
         privatemsgs.id, 
         privatemsgs.useradn, 
         privatemsgs.useraid, 
         privatemsgs.title, 
         privatemsgs.created, 
         privatemsgs.timee, 
         privatemsgs.isread, 
         u.photo AS creatorphoto, 
         privatemsgs.relatedto 
        FROM privatemsgs 
        LEFT JOIN 
         users AS u ON(privatemsgs.useraid = u.id) 
        WHERE userbid='$myid' 
         AND relatedto=0 and bdel=1) 
        UNION 
        (SELECT 
         privatemsgs.id, 
         privatemsgs.useradn, 
         privatemsgs.useraid, 
         privatemsgs.title, 
         privatemsgs.created, 
         privatemsgs.timee, 
         privatemsgs.isread, 
         u.photo AS creatorphoto, 
         rel.relatedto 
        FROM privatemsgs AS rel 
         JOIN privatemsgs ON(rel.relatedto = privatemsgs.id) 
         LEFT JOIN 
         users AS u ON(rel.useraid = u.id) 
        WHERE rel.userbid='$myid' 
        )) privatemsgs 
        GROUP BY id 
        ORDER BY timee DESC 

我有雙號 「2」。第一個是「isread = 0」，第二個是「isread = 1」。

當我補充說：「通過ID組」，我有（2號線）

但我需要輸出到顯示isread = 1（如3號線）

如何解決呢？

Answer 1

在*附近添加MAX（isread）。 GROUP BY僅適用於聚合函數