Question

I have a typical question with a twist.

I need to modify the following T SQL query. Currently it only looks in one table for information. I need to look into two tables with identical columns for information. One table contains current employees and one contains former employees

SELECT t.net_Id
      ,e.fname
      ,e.lname
FROM tblTrackingEmployee t
    join view_employee e 
        on e.net_id = t.net_id
where trackingid = @trackingId
and empType = @empType

What I was thinking of doing is using a union to look in both. An employee will either appear in one table or the other, it will never be in both.

SELECT t.net_Id
      ,e.fname
      ,e.lname
FROM tblTrackingEmployee t
    JOIN view_employee e
        ON e.net_id = t.net_id
WHERE trackingid = @trackingId
AND empType = @empType
union 
SELECT t.net_Id
      ,fe.fname
      ,fe.lname
FROM tblTrackingEmployee t
      JOIN view_employee fe 
             ON fe.net_id = t.net_id
WHERE trackingid = @trackingId
AND empType = @empType

However here is the twist, I need to know if the person/s returned are current or former employees. Is there a way to add a column to the returned table that has a 1 if its a current employee or 0 if its a former employee? Each trackingId can potentially contain both types of employees.

Answer 1

Add a constant column to each SELECT clause – you can alias it:

SELECT t.net_Id
      ,e.fname
      ,e.lname
      ,'Current' AS Type
FROM tblTrackingEmployee t
    JOIN view_employee e
        ON e.net_id = t.net_id
WHERE trackingid = @trackingId
AND empType = @empType
union 
SELECT t.net_Id
      ,fe.fname
      ,fe.lname
      ,'Former'
FROM tblTrackingEmployee t
      JOIN view_formerEmployee fe 
             ON fe.net_id = t.net_id
WHERE trackingid = @trackingId
AND empType = @empType