Question: What is the percentage of employees who work the night shift?
SQL: 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