What is the percentage of employees who work the night shift?
percentage = DIVIDE(SUM(Name = 'Night')), (COUNT(ShiftID)) as percentage;
SELECT CAST(SUM(CASE WHEN T1.Name = 'Night' THEN 1 ELSE 0 END) AS REAL) * 100 / COUNT(T2.BusinessEntityID) FROM Shift AS T1 INNER JOIN EmployeeDepartmentHistory AS T2 ON T1.ShiftId = T2.ShiftId