Un poco desordenado y lo más probable es que se pueda mejorar
;With RawData AS
(
select * from @t
)
,Ranked1 as
(
select *, RANK() OVER (PARTITION BY GroupId, RowID ORDER BY ID, GroupId, RowID) R from @t
)
,Ranked2 as
(
select *, R - RANK() OVER (PARTITION BY GroupId, RowID ORDER BY ID, GroupId, RowID) R2 from Ranked1
where Data is null
)
,Ranked3 as
(
select MIN(ID) as MinID, GroupId, RowID, R2, COUNT(*) C2 from Ranked2
group by GroupId, RowID, R2
)
,Ranked4 as
(
select RD.ID, RD.GroupId, RD.RowID, ISNULL(Data, C2) as C3 from RawData RD
left join Ranked3 R3 on RD.ID = R3.MinID and RD.GroupId = R3.GroupId and RD.RowID = R3.RowID
where ISNULL(Data, C2) is not null
)
,Grouped as
(
select GroupId, RowID,
(
select isnull(C3, '') from Ranked4 as R41
where R41.GroupId = R42.GroupId and R41.RowID = R42.RowID
order by GroupId, RowID for xml path('')
) as C4
from Ranked4 as R42
group by GroupId, RowID
)
select GroupId,
stuff((
select ',' + C4 from Grouped as G1
where G1.GroupId = G2.GroupId
order by GroupId for xml path('')
), 1, 1, '')
from Grouped G2
group by GroupId
