您可能必须返回 SQL 并创建要求和的列。
使用您的示例:
select
GID,
UID,
Cost,
case when row_number() over(partition by GID,UID ORDER BY GID,UID,Cost) = 1 then Cost else 0 end as firstCostGroup
from
(
select 'a' as GID, 1 as UID, 100 as Cost
union
select 'a', 1, 101
union
select 'a', 2, 200
union
select 'a', 2, 201
union
select 'b', 3, 300
union
select 'b', 3, 301
) as rawdata
row_number 函数需要 SQL 2005 或更高版本。
SQL 2000 的解决方法类似于
drop table #RawData
go
drop table #RawDataFirstRows
GO
create table #RawData
(
id int identity(1,1),
GID varchar(10),
UID int,
Cost int
)
insert into #RawData
select 'a' as GID, 1 as UID, 100 as Cost
union
select 'a', 1, 101
union
select 'a', 2, 200
union
select 'a', 2, 201
union
select 'b', 3, 300
union
select 'b', 3, 301
create table #RawDataFirstRows
(
id int
)
insert into #RawDataFirstRows
select
rd.id
from #RawData rd
where
rd.id = (select top 1 id from #RawData rw where rd.uid = rw.uid and rd.gid = rw.gid order by rw.gid,rw.uid)
select
rd.GID, rd.UID, rd.Cost, case when rw.id is null then 0 else 1 end as firstCostGroup
from
#RawData rd
left join
#RawDataFirstRows rw on rd.id = rw.id
请注意,where 子句中的嵌套查询非常低效,因为它必须为 #Rawdata 表中的每一行调用该查询。完成工作,但代价是什么?
如果它不会导致数据生产级别的性能问题,那么您可能会没事。