SELECT e.FirstName + ' ' + e.LastName AS Name,
        CASE WHEN f.CountUsers IS NULL THEN 0 ELSE f.CountUsers END AS [Users Number]
FROM Employees AS e
LEFT JOIN (
    SELECT r.EmployeeId, COUNT(r.UserId) AS CountUsers
    FROM(
        SELECT EmployeeId, UserId
        FROM Reports
        WHERE EmployeeId IS NOT NULL
        GROUP BY EmployeeId, UserId
    ) as r
    GROUP BY r.EmployeeId
) AS f ON f.EmployeeId = e.Id
ORDER BY f.CountUsers DESC, e.FirstName + ' ' + e.LastName