Select rows with same value in one column but different value in another column - sql

Question

I've been trying to build this query but am new to SQL so I'd really appreciate some help.
In the below table example, I have a Customer Code, a linked Customer Code (which is used to link a child customer to a parent customer), a salesperson, and other irrelevant columns. The goal is to have one Salesperson for each parent customer and it's children. So in the example, CustCode #100 is the parent of itself, #200, #500, and #800. All of these accounts have the same Salesperson (JASON) which is perfect. But for CustCode #300, it is the parent of itself, #400, and #600. However, there isn't one salesperson assigned - its both JIM and SUZY. I want to build a query that shows all accounts for this example. Basically, accounts where the Salesperson field isn't the same value for all of it's child customers.
I tried a Where clause for Salesperson <> Salesperson but its not showing up right.
+-----------+-----------------+------------+----------------------+
| CustCode | Linked CustCode | Salesperson| additional columns...|
+-----------+-----------------+------------+----------------------+
| 100 | 100 | JASON | ... |
| 200 | 100 | JASON | ... |
| 300 | 300 | JIM | ... |
| 400 | 300 | JIM | ... |
| 500 | 100 | JASON | ... |
| 600 | 300 | SUZY | ... |
| 700 | NULL | JIM | ... |
| 800 | 100 | JASON | ... |
+-----------+-----------------+------------+----------------------+
Thanks so much for your help!

Answer 1

You can do self join on the table.
select distinct r2.* from
table r1
join table r2
on
r1.linkedcustcode = r2.linkedcustcode and r1.salesperson <> r2.salesperson

Answer 2

This solution uses a recursive CTE first to build the hierarchy and find the leading code for each row, even if a linked code points to a row which is pointing to an upper row itself.
The final query shows the count of different Salespersons:
DECLARE #tbl TABLE(CustCode INT,[Linked CustCode] INT,Salesperson VARCHAR(100));
INSERT INTO #tbl VALUES
(100,100,'JASON')
,(200,100,'JASON')
,(300,300,'JIM')
,(400,300,'JIM')
,(500,100,'JASON')
,(600,300,'SUZY')
,(700,NULL,'JIM')
,(800,100,'JASON');
--The query
WITH CleanUp AS
(
SELECT CustCode
,CASE WHEN [Linked CustCode]=CustCode THEN NULL ELSE [Linked CustCode] END AS [Linked CustCode]
,Salesperson
FROM #tbl
)
,recCTE AS
(
SELECT CustCode AS LeadingCode,CustCode,[Linked CustCode],Salesperson
FROM CleanUp
WHERE [Linked CustCode] IS NULL
UNION ALL
SELECT recCTE.LeadingCode,t.CustCode,t.[Linked CustCode],t.Salesperson
FROM recCTE
INNER JOIN CleanUp AS t ON t.[Linked CustCode]=recCTE.CustCode
)
SELECT LeadingCode,COUNT(DISTINCT Salesperson) AS CountSalesperson
FROM recCTE
GROUP BY LeadingCode
The result
LeadingCode CountSalesperson
100 1
300 2
700 1