Suppose you receive the following two tables:

DEPARTMENT (DepartmentName, BudgetCode)
EMPLOYEE (EmployeeNumber, EmployeeLastName, EmployeeFirstName, Email, DepartmentName)
and you conclude that EMPLOYEE.DepartmentName is a foreign key to DEPARTMENT.DepartmentName. Show SQL for determining whether the following referential integrity constraint has been enforced:
EMPLOYEE.DepartmentName must exist in DEPARTMENT.DepartmentName