被授予references权限后的revoke测试

文档课题：被授予references权限后的revoke测试.
> show user
USER is "ORA1"
> grant references on dept01 to leo;
> grant select on dept01 to leo;
> conn leo/leo@orclpdb;
> select * from user_tab_privs_recd;

OWNER           TABLE_NAME GRANTOR    PRIVILEGE            GRA HIE COM TYPE       INH
--------------- ---------- ---------- -------------------- --- --- --- ---------- ---
ORA1            DEPT01     ORA1       SELECT               NO  NO  NO  TABLE      NO
ORA1            DEPT01     ORA1       REFERENCES           NO  NO  NO  TABLE      NO
说明：可以看到用户leo被用户ora1授予select、references权限.
> select * from ora1.dept01;
DEPARTMENT_ID DEPARTMENT_NAME                MANAGER_ID LOCATION_ID
------------- ------------------------------ ---------- -----------
           10 Administration                        200        1700
           20 Marketing                             201        1800
           50 Shipping                              124        1500
           60 IT                                    103        1400
           80 Sales                                 149        2500
           90 Executive                             100        1700
          110 Accounting                            205        1700
          190 Contracting                                      1700
   1011490290 Support                                          2500
          400 support                                          2500
          410 support                                          2500
11 rows selected.
> create table emp (empid number,department_id number);
> alter table emp add constraint fk_emp_deptid foreign key (department_id) references ora1.dept01;
> select table_name,constraint_name from user_constraints;
TABLE_NAME      CONSTRAINT_NAME
--------------- --------------------
EMP           FK_EMP_DEPTID
> conn ora1/ora1@orclpdb;
> revoke references on dept01 from leo;
revoke references on dept01 from leo
*
ERROR at line 1:
ORA-01981: CASCADE CONSTRAINTS must be specified to perform this revoke
说明：此时无法revoke references权限，因为用户leo创建了一个引用dept01(department_id)的表emp.
如果非要revoke references权限，需加cascade constraints.
> revoke references on dept01 from leo cascade constraints;

Revoke succeeded.
> conn leo/leo@orclpdb
> select table_name,constraint_name from user_constraints;

no rows selected
说明：revoke references权限后，约束一并被拿掉.