Using the information given you can do something like this

SELECT *

FROM OneDatabase.dbo.EmployeeLocation el

JOIN SomeDatabase.dbo.Location l ON el.locationcode = l.locationcode

JOIN AnotherDatabase.dbo.Employee e ON el.employeeID = e.employeeID

AND l.locationID = e.locationID

You need to change the names of the databases and include the fields that you need insteadof the asterisk.

I'm assuming that your databases are on the same server.