Identify table data is retrieved from - tsql

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

Answer 2

Let me get this straight, you have two tables, one has current employees one has former employees? This was a bad idea already you could have had one table with a status ('Active' / 'Inactive'). In any event just add a field, like an int, that you want to each query
SELECT
0 AS TheField,
....
FROM
Table
UNION ALL
SELECT
1 AS TheField,
...
FROM
table

Answer 3

You can also sort by the Status if you would like:
SELECT U.* FROM
(
SELECT t.net_Id AS ID
,e.fname AS FName
,e.lname AS LName
,'Current' AS EmployStatus
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 AS ID
,fe.fname AS FName
,fe.lname AS LName
,'Former' AS EmployStatus
FROM tblTrackingEmployee t
JOIN view_formerEmployee fe
ON fe.net_id = t.net_id
WHERE trackingid = #trackingId
AND empType = #empType
) AS U
ORDER BY U.EmployStatus