SQL在左联接上获取最大ID字段

尝试

SELECt messages.*, T2.photoFROM messagesLEFT JOIN (SELECt userid, MAX(id) AS maxidFROM tblimagesGROUP BY userid) AS T1ON messages.user_id = T1.useridLEFT JOIN tblimages AS T2ON T2.id = T1.maxidORDER BY messages.msg_id DESC

会在tblimages中为每个用户找到max（id），然后使用该值将每个用户加入该用户的最新照片。