从上一行中拉出非空白

问题描述

我有以下数据（前3列）。我想创建第四列-1597437386198 08/14/2020/ 20:36:26 。

newstatus列的逻辑是

1. 每个pk2
2. 如果列newstatus为空，则从 status是新的还是旧的最新行。

因为第3行从第2行获得新值，而第9行从第7行获得旧值，所以第8行被忽略，因为它具有值status

ignore

解决方法

嗯。 。 。使用outer apply

可能最简单

select t.*,(case when status is null then t2.status end) as new_status
from t outer apply
     (select top (1) t2.*
      from t t2
      where t2.pk2 = t.pk2 and t2.status in ('old','new') and
            t2.pk1 < t.pk1
      order by t2.pk1 desc
     ) t2;

实际上有一种无需子查询即可完成此操作的方法。 。 。这可能是最有效的方法：

select t.*,(case when status is null and
                  max(case when status = 'old' then pk1 end) over (partition by pk2 order by pk1) >
                  max(case when status = 'new' then pk2 else 0 end order by pk1) over (partition by pk2)
             then 'old'
             when status is null and
                  max(case when status = 'new' then pk1 end) over (partition by pk2 order by pk1) >
                  max(case when status = 'old' then pk2 else 0 end) over (partition by pk2 order by pk1)
             then 'new'
      end) as new_status
from t;

,

您可以使用窗口功能。

这个想法是建立每当具有“新”或“旧”状态时其累积计数就增加的行组。然后，您可以在需要时使用first_value()访问相应的状态。

select 
    t.*,case when status is null and grp > 0
        then first_value(status) over(partition by pk2,grp order by pk1)
        else status
    end as new_status
from (
    select 
        t.*,sum(case when status in ('old','new') then 1 else 0 end)
            over(partition by pk2 order by pk1) grp
    from mytable t
) t

,

您可以使用此脚本

WITH OuterT AS
(
SELECT *,ROW_NUMBER() OVER(PARTITION BY pk2 ORDER BY pk1) num FROM tbl
)
SELECT pk1,[Status],pk2,(CASE WHEN num=1 or [Status] !='' THEN ''
WHEN num !=1 THEN
(SELECT TOP 1 innerT.[Status] FROM OuterT innerT WHERE innerT.pk2 =OuterT.pk2 and ([status] ='new' or [status] ='old') and num != 1 and innerT.pk1 < OuterT.pk1  ORDER BY pk1 DESC)
END) newstatus
FROM OuterT

工作原理：

我用common_table_expression命名为OuterT

WITH OuterT AS
(
SELECT *,ROW_NUMBER() OVER(PARTITION BY pk2 ORDER BY pk1) num FROM tbl
)

然后我用ROW_NUMBER命名为num

OuterT的内部结果是：

然后，我使用了CASE，其中包含基于OuterT的逻辑

(CASE WHEN num=1 or [Status] !='' THEN ''
WHEN num !=1 THEN
(SELECT TOP 1 innerT.[Status] FROM OuterT innerT WHERE innerT.pk2 =OuterT.pk2 and ([status] ='new' or [status] ='old') and num != 1 and innerT.pk1 < OuterT.pk1  ORDER BY pk1 DESC)
END) newstatus

最终结果是：

注意：如果要使用脚本，只需将“ tbl”替换为表名

,

这是一所古老的学校，没有开窗功能，也没有外部应用。

drop table if exists #testTable;
go
create table #testTable(
  pk        int unique not null,[status]  varchar(20),pk2       int not null);

insert into #testTable(pk,[status],pk2) values
(1,null,1),(2,'new',(3,(4,'ignore',(5,(6,2),(7,'old',(8,(9,(10,2);   

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