AALTER TABLE salary ADD CONSTRAINT fk_employee_id_01 FOREIGN KEY(employee_id)REFERENCES employees(employee_id)
BALTER TABLE salary ADD CONSTRAINT fk_employee_id_ FOREIGN KEY BETWEEN salary(employee_id)AND employees(employee_id)
CALTER TABLE salary FOREIGN KEY CONSTRAINT fk_employee_id_REFERENCES employees(employee_id)
DALTER TABLE salary ADD CONSTRAINT fk_employee_id_FOREIGN KEY salary(employee_id)=employees(employee_id)