TSQL - 困难的分组

Question

请参阅fiddle：http://sqlfiddle.com/#!6/e6768/2

我有数据，如下：

DRIVER  DROP
1       1
1       2
1       ReturnToBase
1       4
1       5
1       ReturnToBase
1       6
1       7    
2       1
2       2
2       ReturnToBase
2       4

我正在尝试对我的数据进行分组，因此对于每个车手，每组 return 到基地都有一个分组编号。

我的输出应该是这样的：

DRIVER      DROP           GROUP
1            1              1
1            2              1
1            ReturnToBase   1
1            4              2
1            5              2
1            ReturnToBase   2
1            6              3
1            7              3
1            ReturnToBase   3               
2            1              1           
2            2              1
2            ReturnToBase   1   
2            4              2

我试过结合窗口函数得到这个结果，但到目前为止我还差得远

以下是我目前所拥有的，它不应该起作用我试图弄清楚它是如何完成的，如果可能的话。

SELECT 
    ROW_NUMBER() OVER (Partition BY Driver order by Driver Desc) rownum,
    Count(1) OVER (Partition By Driver Order By Driver Desc) counter,
    Count
    DropNo,
    Driver,
    CASE DropNo 
       WHEN 'ReturnToBase' THEN 1 ELSE 0 END AS EnumerateRound
FROM 
    Rounds

Answer 1

您可以使用以下查询：

SELECT id, DRIVER, DROPno, 
       1 + SUM(flag) OVER (PARTITION BY DRIVER ORDER BY id) -
       CASE 
          WHEN DROPno = 'ReturnToBase' THEN 1 
          ELSE 0 
       END AS grp       
FROM (
  SELECT id, DRIVER, DROPno, 
         CASE 
            WHEN DROPno = 'ReturnToBase' THEN 1 
            ELSE 0 
         END AS flag
  FROM rounds ) AS t

Demo here

此查询使用 SUM 的窗口版本和 OVER 子句中的 ORDER BY 来计算运行总数。此版本的 SUM 可从 SQL Server 2012 AFAIK 开始使用。

为了获得正确的 GROUP 值，我们只需要稍微调整这个运行总值。

编辑：（归功于@Conrad Frix）

使用 CROSS APPLY 而不是内联视图可以大大简化事情：

SELECT id, DRIVER, DROPno, 
       1 + SUM(x.flag) OVER (PARTITION BY DRIVER ORDER BY id) - x.flag
FROM rounds
CROSS APPLY (SELECT CASE WHEN DROPno = 'ReturnToBase' THEN 1 ELSE 0 END) AS x(flag)

Demo here

Answer 2

在您的示例中添加了顺序 ID 列以用于递归 CTE：

with cte as (
select ID,DRIVER,DROPno,1 as GRP
FROM rounds
where ID = 1
union all
select a.ID
,a.DRIVER
,a.DROPno
,case when b.DROPno = 'ReturnToBase' 
      or b.DRIVER <> a.DRIVER then b.GRP + 1 
      else b.GRP end
from rounds a
  inner join cte b
    on a.ID = b.ID + 1
)

select * from cte

SQL Fiddle

TSQL - 困难的分组

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