Question

I have a SQL table that I cannot change the structure of.

The table Employee_Team has 5 columns: TeamID, Employee1, Employee2, Employee3 and Employee4. The fields of columns Employee1, Employee2, Employee3 and Employee4 contain an EmployeeID. Each Employee ID has a City in the table Employee. It’s possible to have multiple employees on the same row of Employee_Team that are living in the same town. There will always be at least 1 employee that will live in the town I’m looking for.

example http://www.atriasoft.com/table.png

Example:

I want the first employee that lives in New York. In the case of TeamID 01, it will be Employee2 (I don’t want Employee 4 even though his city is New York) and for the case of TeamID 02, it will be Employee1 (I still don’t want the second employee that lives in New York).

I currently have a code that gives me every employee that lives in New York:

SELECT * 
  FROM Employee_Team
 INNER JOIN Employees
    ON Employees.EmployeeID = Employee_Team.Employee1 OR
       Employees.EmployeeID = Employee_Team.Employee2 OR
       Employees.EmployeeID = Employee_Team.Employee3 OR
       Employees.EmployeeID = Employee_Team.Employee4
 WHERE Employees.City = ‘New York’

What I am looking for is a code that takes only the first employee living in New York.
Any hints will be much appreciated!

Answer 1

You actually can safely “change” the definition of your table, virtually, by using it as the basis of a view:

 CREATE VIEW NormalTeams (TeamID, EmployeeID, TeamMemberNumber) AS
     SELECT TeamID, Employee1, 1 FROM Employee_TEAM UNION ALL
     SELECT TeamID, Employee2, 2 FROM Employee_TEAM UNION ALL
     SELECT TeamID, Employee3, 3 FROM Employee_TEAM UNION ALL
     SELECT TeamID, Employee4, 4 FROM Employee_TEAM

Now, NormalTeams will let you SELECT the data the way you expect to be able to:

 SELECT TeamID, MIN(TeamMemberNumber)
    FROM NormalTeams T INNER JOIN Employees E ON T.EmployeeiD = E.EmployeeID
    WHERE E.City = 'New York'
    GROUP BY TeamID

will give you the first team member “number” for New York.

 SELECT TeamID, City, MIN(TeamMemberNumber)
    FROM NormalTeams T INNER JOIN Employees E ON T.EmployeeiD = E.EmployeeID
    GROUP BY TeamID, City

will give you the more general solution for every City / Team combination.

You can join these results back to NormalTeams to get the employee ID.