计算 SQL Server 中某个值的最大连续出现次数

Question

我有一张包含球员、结果和 ID 的表格：

Player | Result | ID
---------------
An     | W      | 1
An     | W      | 1
An     | L      | 0
An     | W      | 1
An     | W      | 1
An     | W      | 1
Ph     | L      | 0
Ph     | W      | 1
Ph     | W      | 1
Ph     | L      | 0
Ph     | W      | 1

“W”的 ID 始终为 1，

我需要创建一个查询来计算每个玩家连续“W”的最大数量：

Player | MaxWinStreak
---------------------
An     | 3    
Ph     | 2

我尝试使用 Rows Unbounded Preceeding 但我只能让它计算 Ws 的最大总数，而不是连续计算

    Select
    t2.player
    ,max(t2.cumulative_wins) As 'Max'

    From

    (   Select 
            t.Player
            ,Sum(ID) Over (Partition By t.Result,t.player 
             Order By t.GameWeek Rows Unbounded Preceding) As cumulative_wins

        From
             t  

             ) t2

    Group By
    t2.player

我可以采取不同的方法吗？

Answer 1

您需要一列来指定排序。 SQL 表代表 无序 集合。在下面的查询中，? 代表该列。

您可以使用行号的差异来获得每个连胜：

select player, count(*) as numwins
from (select t.*,
             row_number() over (partition by player order by ?) as seqnum, 
             row_number() over (partition by player, result order by ?) as seqnum_r 
      from t
     ) t
where result = 'W'
group by player, (seqnum - seqnum_r);

然后你可以得到最大值：

select player, max(numwins)
from (select player, count(*) as numwins
      from (select t.*,
                   row_number() over (partition by player order by ?) as seqnum, 
                   row_number() over (partition by player, result order by ?) as seqnum_r 
            from t
           ) t
      where result = 'W'
      group by player, (seqnum - seqnum_r)
     ) pw
group by player;