在SQL Server 2008中排序和重新設置

Question

我實際上是SQL Server 2008的新手，我嘗試對錶中的數字進行排序和重新設置。來源是這樣的：

Row Refrec FLAG 
1  5  NULL 
2  4  X  
3  3  NULL 
4  2  NULL 
5  1  Y  
6  5  A  
7  4  B   
8  3  NULL 
9  2  NULL 
10 1  NULL 

結果應該是這樣的：

Row Refrec FLAG SEQUENCE 
1  5  NULL NULL 
2  4  X  0 
3  3  NULL 1 
4  2  NULL 2 
5  1  Y  0 
6  5  A  0 
7  4  B  0  
8  3  NULL 1 
9  2  NULL 2 
10 1  NULL 3 

謝謝！

Answer 1

看起來您想要枚舉NULL值的序列值，並將所有其他值設置爲0。我不確定爲什麼第一個值是NULL，但這很容易修復。

下可以做你想做的：

select t.*, 
     (case when flag is not null then 0 
      else row_number() over (partition by seqnum - row order by row) 
     end) as Sequence 
from (select t.*, row_number() over (partition by flag order by row) as seqnum 
     from table t 
    ); 

如果你真正關心的第一個值：

select t.*, 
     (case when row = 1 then NULL 
      when flag is not null then 0 
      else row_number() over (partition by seqnum - row order by row) 
     end) as Sequence 
from (select t.*, row_number() over (partition by flag order by row) as seqnum 
     from table t 
    );