Assign ID based on commonality/groups - sql

Question

I've put together what I view to be overly complicated SQL to get to what I'm after. I'm hoping for insight into a quicker and less complicated method.
What I'm after is the ability to assign an ID to groups of data where there is common groups of data across two columns.
For example I have the following subset of data:
CustID PartID RplcID
28 4 4
28 4 16
28 4 17
28 16 4
28 16 16
28 16 17
28 17 4
28 17 16
28 17 17
I want to create an ID for CustID=28 where there is overlap in the RplcID and PartID. So in this example, PartID 4, 16, 17 all have RplcIDs in common (4, 16, 17). As such, all of these pairs should have the same ID.
The method I'm using works (and is faster with temp tables instead of solely using CTEs) except for large datasets this thing is S-L-O-W. I'm sure there's a more efficient method out there and hoping someone can lend their expertise.
I'm outlining my current approach for as much clarity into my muddled thinking as possible.
STEP 1
Generate temporary ID using DENSE_RANK() partitioned by CustID, ordered by PartID.
RowID CustID PartID RplcID
1 28 16 16
1 28 17 16
1 28 4 16
2 28 16 17
2 28 17 17
2 28 4 17
3 28 16 4
3 28 17 4
3 28 4 4
STEP 2:
Then use these results and aggregate the PartIDs by using XML to create a comma separated string with which to group by.
RowID CustID RplcID PartIDS
4 28 16 16,17,4
4 28 17 16,17,4
4 28 4 16,17,4
STEP 3:
And finally split out these groups using the assigned ID by parsing the XML.
RowID CustID PartID RplcID
4 28 16 16
4 28 16 17
4 28 16 4
4 28 17 16
4 28 17 17
4 28 17 4
4 28 4 16
4 28 4 17
4 28 4 4
And the entirety of the SQL:
DECLARE #Parts TABLE
(
CustID VARCHAR(10),
PartID VARCHAR(10),
RplcID VARCHAR(10)
)
Insert Into #Parts VALUES
('26','19','93'),('26','19','63'),
('26','31','93'),('26','31','63'),('26','32','93'),('26','32','63'),('26','33','93'),('26','33','63'),('26','34','93'),
('26','34','63'),('26','35','93'),('26','35','63'),('26','36','93'),('26','36','63'),('26','37','93'),('26','37','63'),
('26','38','93'),('26','38','63'),('26','39','93'),('26','39','63'),('27','40','95'),('27','41','94'),
('27','41','95'),('27','42','94'),('27','42','95'),('27','43','94'),('27','43','95'),('27','44','94'),('27','44','95'),
('27','45','94'),('27','45','95'),('27','46','94'),('27','46','95'),('27','47','94'),('27','47','95'),('27','48','94'),
('27','48','95'),('27','49','94'),('27','49','95'),('27','50','94'),('27','50','95'),('27','17','94'),('27','17','95'),
('27','51','94'),('27','51','95'),('27','52','94'),('27','52','95'),('27','53','94'),('27','53','95'),('27','54','94'),
('27','54','95'),('27','33','94'),('27','33','95'),('27','55','94'),('27','55','95'),('27','34','94'),('27','34','95'),
('27','56','94'),('27','56','95'),('27','35','94'),('27','35','95'),('27','57','94'),('27','57','95'),('27','58','94'),
('27','58','95'),('27','59','94'),('27','59','95'),('27','37','94'),('27','37','95'),('27','60','94'),('27','60','95'),
('27','61','94'),('27','61','95'),('27','62','94'),('27','62','95'),('27','63','94'),('27','63','95'),('27','64','94'),
('27','64','95'),('27','3','96'),('27','3','97'),('27','3','98'),('27','3','99'),('27','3','100'),('28','4','4'),
('28','4','16'),('28','4','17'),('28','16','4'),('28','16','16'),('28','16','17'),('28','17','4'),('28','17','16'),
('28','17','17')
;
--Step 1: Create the initial ID
SELECT DISTINCT DENSE_RANK()
OVER(
partition BY r.CustID
ORDER BY r2.RplcID) AS RowID,
r.CustID,
r.BuyID,
r2.RplcID
INTO #tmp
FROM #Parts r
JOIN #Parts r1
ON r.CustID = r1.CustID
AND r.RplcID = r1.RplcID
JOIN #Parts r2
ON r.CustID = r2.CustID
AND r1.BuyID = r2.BuyID
--Step 2: Group the BuyIDs
SELECT DENSE_RANK()
OVER(
ORDER BY CustID, BuyIDs) AS RowID,
*
INTO #tmp2
FROM (SELECT CustID,
Rtrim(RplcID) RplcID,
Stuff((SELECT ',' + Rtrim(BuyID)
FROM #tmp RSLT2
WHERE RSLT2.ROWID = RSLT.ROWID
AND RSLT2.CustID = RSLT.CustID
FOR xml path('')), 1, 1, '') [BuyIDs]
FROM #tmp RSLT
GROUP BY RSLT.CustID,
RSLT.ROWID,
RSLT.RplcID)A
--Step 3: Using the grouped BuyIDs, split the strings using XML and assign RowID
SELECT RowID,
CustID,
BuyID,
RplcID
INTO #tmp3
FROM (SELECT RowID,
CustID,
n.r.value('.','varchar(10)') AS BuyID,
RplcID
FROM #tmp2
CROSS APPLY(SELECT Cast('<r>' + Replace(BuyIDs, ',', '</r><r>')
+ '</r>' AS XML)) AS S(xmlcol)
CROSS APPLY s.xmlcol.nodes('r') AS n(r))A
Order by RowID
Select * from #tmp3 where CustID='28'
Select distinct BuyID
from #tmp3
where CustID='28'
Select distinct RplcID
from #tmp3
where CustID='28'