sql - 如何在sql中通过两列匹配生成行号分区

Question

表1

---------------------------------------------------------
Id      Date        Qty      ReOrder
---------------------------------------------------------
1       1-1-18      1        3
2       2-1-18      0        3
3       3-1-18      2        3
4       4-1-18      3<      >3
5       5-1-18      2        3
6       6-1-18      0        3
7       7-1-18      1        3
8       8-1-18      0        3
---------------------------------------------------------

我想要下面的结果

---------------------------------------------------------
Id      Date        Qty      ReOrder
---------------------------------------------------------
1       1-1-18      1        3
5       5-1-18      2        3
---------------------------------------------------------

如果 ReOrder 与 Qty 不同，则在 reorder=Qty 之后日期将相同

Answer 1

您可以将累积方法与row_number()函数一起使用：

select top (1) with ties *
from (select *, max(case when qty = reorder then 'v' end) over (order by id desc) grp
      from table
     ) t
order by row_number() over(partition by grp order by id); 

不幸的是，这将需要SQL Server，但您也可以这样做：

select *
from (select *, row_number() over(partition by grp order by id) seq
      from (select *, max(case when qty = reorder then 'v' end) over (order by id desc) grp
            from table
           ) t
     ) t
where seq = 1;