DEPARTMENT 表包含以下列: DEPT_ID NUMBER, Primary Key DEPT_ABBR VARCHAR2(4) DEPT_NAME VARCHAR2(30) MGR_ID NUMBER EMPLOYEE 表包含以下列: EMPLOYEE_ID NUMBER EMP_LNAME VARCHAR2(25) EMP_FNAME VARCHAR2(25) DEPT_ID NUMBER JOB_ID NUMBER MGR_ID NUMBER SALARY NUMBER(9,2) HIRE_DATE DATE 请评估以下语句: ALTER TABLE employee ADD CONSTRAINT REFERENTIAL (mgr_id) TO department(mgr_id); 是以下哪个说法()