sql

WITH Grouped (TownName, EmployeesCount)
AS
(
    SELECT t.Name, COUNT(e.EmployeeID) AS EmployeesCount FROM Employees e
        JOIN Addresses a ON e.AddressID = a.AddressID
        JOIN Towns t ON a.TownID = t.TownID
        GROUP BY t.Name
)

SELECT TownName, EmployeesCount
FROM Grouped g
WHERE g.EmployeesCount =
    (SELECT MAX(s.EmployeesCount) AS MaxCount
    FROM Grouped s)