Question

我有2张这样的表

聊天列表表 COLUMNS：ID INTEGER PRIMARY KEY，PHONE，DISPLAYNAME，SESSIONID

消息表 COLUMNS：ID INTEGER PRIMARY KEY，[DATETIME]，[FROM]，[TO]，[TYPE]，[MESSAGE]，[ISGROUP]，[GROUPID]，[READED]，[SESSIONID]，[MESSAGEID]，[DISPLAYNAME]

我想从消息表到聊天列表加入

获取最后一条记录

SELECT m.ID as MID, m.DATETIME, c.ID, c.DISPLAYNAME, c.PHONE, c.SESSIONID, m.TYPE, m.MESSAGE
FROM [CHATLIST] as c
   , [MESSAGES] as m
WHERE m.SESSIONID = c.SESSIONID
GROUP BY c.SESSIONID
ORDER BY MID DESC

它不能正常工作

Answer 1

您忘记添加LIMIT

SELECT m.ID as MID, m.DATETIME, c.ID, c.DISPLAYNAME, c.PHONE, c.SESSIONID, 
m.TYPE, m.MESSAGE
    FROM [CHATLIST] as c, [MESSAGES] as m
    WHERE m.SESSIONID = c.SESSIONID
    GROUP BY c.SESSIONID
    ORDER BY MID DESC
    LIMIT 1

Web SQL从第二个表获取最后一条记录

1 个答案: