Selecting Same Column Twice Using Alias Table - sql

Question

Below are examples of the tables I am working with. These only represent the columns relevant to my query
_Requirements
RequirementID fkOwningWsID
-------------------------------------------
REQ-RPT-01 1
REQ-RPT-02 2
_Workstream
pk WsNm
-------------------------------------------
1 Workstream1
2 Workstream2
mnWorkstream_Leads
fkWsID fkEeID
-------------------------------------------
1 1
1 2
2 1
2 2
The below table is a result of a union. Employees can be from different companies, the below union lists all the employee IDs, the IDs for the employees who are from Company 1 (0 otherwise) and IDs for employees from company 2 (0 otherwise)
qryTrackerAllEeList
EeID Company1_ID Company2_ID
-------------------------------------------
1 1 0
2 0 2
I am attempting to view the following result
RequirementID WsNm Company1_Lead Company2_Lead
--------------------------------------------------------------------
REQ-RPT-01 Workstream1 1 2
REQ-RPT-02 Workstream2 1 2
I have issued the following SQL
SELECT DISTINCT Req.RequirementID, Ws.Wsnm, company1_id.ee_id, company2_id.ee_id
FROM (((([_Requirements] AS Req
INNER JOIN [_Workstream] AS Ws ON Req.fkOwningWsID = Ws.pkWsID)
INNER JOIN [mnWorkstream_Leads] AS wsLeads ON Ws.pkWsID = wsLeads.fkWsID)
LEFT OUTER JOIN qryTrackerAllEeList AS company1 ON wsLeads.fkEeID = company1.Company1_ID)
LEFT OUTER JOIN qryTrackerAllEeList AS company2 ON wsLeads.fkEeID = company2.Company2_ID)
The issue is, however, that I retrieve the following results
RequirementID WsNm Company1_Lead Company2_Lead
--------------------------------------------------------------------
REQ-RPT-01 Workstream1 2
REQ-RPT-01 Workstream1 1
REQ-RPT-02 Workstream2 2
REQ-RPT-02 Workstream2 1
Any suggestions on how to eliminate these duplicative rows and null values?

Answer 1

Use MAX() and GROUP BY to only select the non null values and group them into one row:
SELECT DISTINCT Req.RequirementID, Ws.Wsnm,
MAX(company1_id.ee_id) as Company1_Lead, MAX(company2_id.ee_id) as Company2_Lead,
FROM (((([_Requirements] AS Req
INNER JOIN [_Workstream] AS Ws ON Req.fkOwningWsID = Ws.pkWsID)
INNER JOIN [mnWorkstream_Leads] AS wsLeads ON Ws.pkWsID = wsLeads.fkWsID)
LEFT OUTER JOIN qryTrackerAllEeList AS company1 ON wsLeads.fkEeID = company1.Company1_ID)
LEFT OUTER JOIN qryTrackerAllEeList AS company2 ON wsLeads.fkEeID = company2.Company2_ID)
GROUP BY req.RequirementID, Ws.Wsnm