sql获取连续值最大的成员1

Question

我正在尝试让sql返回memberid 2因为我希望得到连续值最大的成员，即使memberid 1是值1的四倍。

memberid position createdat
======== ======== =========
1        1         9/1/2001
1        1         8/1/2001
2        1         7/1/2001
2        1         6/1/2001
2        1         5/1/2001
1        1         4/1/2001
1        1         3/1/2001

万分感谢你的帮助。

Answer 1

您需要使用参数作为计数器。在下面的@r中，每个行都会递增，只要该成员与前一行（由order by定义）相同，如果它不是同一个成员@r重置为1：

SELECT  MemberID
FROM    (   SELECT  MemberID,
                    Position,
                    CreateDat,
                    @r:=IF(@m = MemberID, @r + 1, 1) AS Consec,
                    @m:= MemberID
            FROM    T,
                    (SELECT @r:= 0) r,
                    (SELECT @m:= 0) m
            ORDER BY CreateDat DESC
        ) t
ORDER BY Consec DESC
LIMIT 1;

<强> Example on SQL Fiddle

修改

稍微调整一下，您可以获得更多信息，例如连续期间的开始和结束时间：

SELECT  MemberID, FirstCreateDat, CreateDat, Consec
FROM    (   SELECT  MemberID,
                    Position,
                    CreateDat,
                    @r:=IF(@m = MemberID, @r + 1, 1) AS Consec,
                    @d:=IF(@m = MemberID, @d, CreateDat) AS FirstCreateDat,
                    @m:= MemberID
            FROM    T,
                    (SELECT @r:= 0) r,
                    (SELECT @m:= 0) m,
                    (SELECT @d:= CAST(NULL AS DATETIME)) d
            ORDER BY CreateDat DESC
        ) t
ORDER BY Consec DESC
LIMIT 1;

<强> Example on SQL Fiddle