Which employee has been in the Engineering Department the longest? Please give his or her firstname and lastname.
length of stay in a department = SUBTRACT(EndDate, StartDate);
SELECT T1.FirstName, T1.LastName FROM Person AS T1 INNER JOIN EmployeeDepartmentHistory AS T2 ON T1.BusinessEntityID = T2.BusinessEntityID INNER JOIN Department AS T3 ON T2.DepartmentID = T3.DepartmentID WHERE T3.Name = 'Engineering' ORDER BY T2.EndDate - T2.StartDate DESC LIMIT 1