Joined 3 Tables in SQL and Getting duplicated records - sql

Question

I have 3 tables and trying to get the data out without having many duplicates. Please check on the image that I sent. This is the desired result. Thanks.
I tried:
EDIT:
All this does is Grab all records from Parts then all the records from Assemblies then all the records in Materials. So the return records is HUGE. Here is the standard SQL Statement that connects these tables together.
SELECT impPartID, impShortDescription, uimpConfigPartID as ConfigID,
imaPartID, immPartID FROM Parts
Left Outer Join PartAssemblies on IMAMETHODID = IMPPARTID and
IMAPARENTASSEMBLYID = 0
Left Outer Join PartMaterials on IMMMETHODID = IMPPARTID and
IMMMETHODASSEMBLYID = 0
So I tried this
Select p.impPartID, p.impShortDescription, p.uimpConfigPartID as ConfigID,
a.imaPartID as Assem, m.immPartID as Materials
from (select p.*, row_number() over (order by (select null)) as seqnum
from parts p where uimpConfigPartID <> ''
) p full join
(select a.*, row_number() over (order by (select null)) as seqnum
from assemblies a
) a
on a.IMAMETHODID = p.impPartID and a.seqnum = p.seqnum full join
(select m.*, row_number() over (order by (select null)) as seqnum
from materials m
) m
on m.IMMMETHODID = coalesce(a.IMAMETHODID, p.impPartID) and
m.seqnum = coalesce(a.seqnum, p.seqnum)

Answer 1

One method uses row_number(), union all and group by:
select p.partid, a.descassembly, m.descmaterial
from (select p.*, row_number() over (order by (select null)) as seqnum
from parts p
) p full join
(select a.*, row_number() over (order by (select null)) as seqnum
from assemblies a
) a
on a.partid = p.partid and a.seqnum = p.seqnum full join
(select m.*, row_number() over (order by (select null)) as seqnum
from materials m
) a
on m.partid = coalesce(a.partid, p.partid) and
m.seqnum = coalesce(a.seqnum, p.seqnum);