[每日一题] OCP1z0-047 :2013-08-24 FLASHBACK—TABLE/PRIMARY KEY(FOREIGN KEY?)......98

 

正确答案：D

 

根据题意如下操作：

一、创建表dept

gyj@OCM> CREATE TABLE DEPT
  2     (DEPTNO NUMBER(2,0),
  3      DNAME VARCHAR2(14),
  4      LOC VARCHAR2(13),
  5      CONSTRAINT PK_DEPT PRIMARY KEY (DEPTNO)
  6    );

Table created.

 

二、创建表emp

gyj@OCM> CREATE TABLE EMP
  2     (EMPNO NUMBER(4,0),
  3      ENAME VARCHAR2(10),
  4      JOB   VARCHAR2(9),
  5      MGR   NUMBER(4,0),
  6      HIREDATE DATE,
  7      SAL   NUMBER(7,2),
  8      COMM  NUMBER(7,2),
  9      DEPTNO NUMBER(2,0),
 10           CONSTRAINT PK_EMP PRIMARY KEY (EMPNO),
 11           CONSTRAINT FK_DEPTNO FOREIGN KEY (DEPTNO)
 12            REFERENCES DEPT (DEPTNO) ENABLE
 13     );

Table created.

 

三、分别向表dept和表emp插入数据

gyj@OCM> insert into dept values(10,'IT',null);

1 row created.

gyj@OCM> insert into dept values(20,'HR',null);

1 row created.
gyj@OCM> insert into dept(DEPTNO,DNAME) values(10,'IT');

1 row created.

gyj@OCM> insert into dept(DEPTNO,DNAME) values(20,'HR');

1 row created.

gyj@OCM> insert into emp(EMPNO,ENAME,DEPTNO) values(1,'KING',10);

1 row created.

gyj@OCM> insert into emp(EMPNO,ENAME,DEPTNO) values(2,'HARI',20);

1 row created.

gyj@OCM> COMMIT;

Commit complete.

 

四、查dept和emp的数据及约束。

gyj@OCM> SELECT deptno,dname FROM dept;

    DEPTNO DNAME
---------- --------------
        10 IT
        20 HR

gyj@OCM> SELECT EMPNO,ENAME,DEPTNO FROM emp;

     EMPNO ENAME          DEPTNO
---------- ---------- ----------
         1 KING               10
         2 HARI               20


gyj@OCM> col CONSTRAINT_NAME for a10
gyj@OCM> col R_CONSTRAINT_NAME for a10
gyj@OCM> col TABLE_NAME for a10
gyj@OCM> col INDEX_NAME for a10
gyj@OCM> select CONSTRAINT_NAME,R_CONSTRAINT_NAME,TABLE_NAME,INDEX_NAME,CONSTRAINT_TYPE,STATUS 
  2  from user_constraints where table_name 
  3  in('EMP','DEPT');

CONSTRAINT R_CONSTRAI TABLE_NAME INDEX_NAME C STATUS
---------- ---------- ---------- ---------- - --------
PK_DEPT               DEPT       PK_DEPT    P ENABLED
PK_EMP                EMP        PK_EMP     P ENABLED
FK_DEPTNO  PK_DEPT    EMP                   R ENABLED

 

五、删除表emp

gyj@OCM> drop table emp;

Table dropped.

 

六、查回收站，可以看出表和索引同时被删除除

gyj@OCM> select  OBJECT_NAME,ORIGINAL_NAME,OPERATION,TYPE ,DROPTIME from recyclebin;

OBJECT_NAME                    ORIGINAL_N OPERATION TYPE       DROPTIME
------------------------------ ---------- --------- ---------- -------------------
BIN$5LNox53pT0PgQ4rZqMD+/Q==$0 PK_EMP     DROP      INDEX      2013-08-24:22:33:40
BIN$5LNox53qT0PgQ4rZqMD+/Q==$0 EMP        DROP      TABLE      2013-08-24:22:33:40

 

七、并且可以查出表emp的外键也被删除了

gyj@OCM> select CONSTRAINT_NAME,R_CONSTRAINT_NAME,TABLE_NAME,INDEX_NAME,CONSTRAINT_TYPE,STATUS 
  2  from user_constraints where table_name 
  3  in('EMP','DEPT');

CONSTRAINT R_CONSTRAI TABLE_NAME INDEX_NAME C STATUS
---------- ---------- ---------- ---------- - --------
PK_DEPT               DEPT       PK_DEPT    P ENABLED

 

八、闪回表emp

gyj@OCM> flashback table emp to before drop;

Flashback complete.

 

九、查回收站，已没信息，说明表和唯一索引（主键约束）都被闪回了，但外键没有被闪回（失去了外键的制约），如下操作。

gyj@OCM> select  OBJECT_NAME,ORIGINAL_NAME,OPERATION,TYPE ,DROPTIME from recyclebin;

no rows selected

gyj@OCM> SELECT EMPNO,ENAME,DEPTNO FROM emp;

     EMPNO ENAME          DEPTNO
---------- ---------- ----------
         1 KING               10
         2 HARI               20
gyj@OCM> col index_name for a50
gyj@OCM> select index_name from user_indexes where table_name='EMP';

INDEX_NAME
--------------------------------------------------
BIN$5LNox53pT0PgQ4rZqMD+/Q==$0

gyj@OCM> col CONSTRAINT_NAME for a40 
gyj@OCM> col index_name for a40
gyj@OCM> select CONSTRAINT_NAME,R_CONSTRAINT_NAME,TABLE_NAME,INDEX_NAME,CONSTRAINT_TYPE,STATUS 
  2  from user_constraints where table_name 
  3  in('EMP','DEPT');

CONSTRAINT_NAME                          R_CONSTRAI TABLE_NAME INDEX_NAME                               C STATUS
---------------------------------------- ---------- ---------- ---------------------------------------- - --------
PK_DEPT                                             DEPT       PK_DEPT                                  P ENABLED
BIN$5LNox53oT0PgQ4rZqMD+/Q==$0                      EMP        BIN$5LNox53pT0PgQ4rZqMD+/Q==$0           P ENABLED

 

十、插入两条数据，第一次插入报错(emp中已存在empno为2的员工了，empno是主键)，第二次插入成功。

gyj@OCM> INSERT INTO emp(EMPNO,ENAME,DEPTNO) values(2,'COTT',10);
INSERT INTO emp(EMPNO,ENAME,DEPTNO) values(2,'COTT',10)
*
ERROR at line 1:
ORA-00001: unique constraint (GYJ.BIN$5LNox53oT0PgQ4rZqMD+/Q==$0) violated


gyj@OCM> INSERT INTO emp(EMPNO,ENAME,DEPTNO) values(3,'ING',55);

1 row created.


gyj@OCM> SELECT EMPNO,ENAME,DEPTNO FROM emp;

     EMPNO ENAME          DEPTNO
---------- ---------- ----------
         1 KING               10
         2 HARI               20
         3 ING                55

 

十一、闪回索引和约束的名称还是：BIN$5LNox53pT0PgQ4rZqMD+/Q==$0和BIN$5LNox53oT0PgQ4rZqMD+/Q==$0，最好修改索引和约束，如下操作：

 

gyj@OCM> ALTER INDEX "BIN$5LNox53pT0PgQ4rZqMD+/Q==$0" RENAME  TO PK_EMP;

Index altered.

gyj@OCM> ALTER TABLE EMP RENAME CONSTRAINT "BIN$5LNox53oT0PgQ4rZqMD+/Q==$0" TO PK_EMP;

Table altered.

gyj@OCM> select CONSTRAINT_NAME,R_CONSTRAINT_NAME,TABLE_NAME,INDEX_NAME,CONSTRAINT_TYPE,STATUS 
  2  from user_constraints where table_name 
  3  in('EMP','DEPT');

CONSTRAINT_NAME                          R_CONSTRAI TABLE_NAME INDEX_NAME                               C STATUS
---------------------------------------- ---------- ---------- ---------------------------------------- - --------
PK_DEPT                                             DEPT       PK_DEPT                                  P ENABLED
PK_EMP                                              EMP        PK_EMP                                   P ENABLED

gyj@OCM> select index_name from user_indexes where table_name='EMP';

INDEX_NAME
----------------------------------------
PK_EMP

呵呵，这样插入记录时报错就能看到正常的约束名称了。

 

 

gyj@OCM>  INSERT INTO emp(EMPNO,ENAME,DEPTNO) values(2,'COTT',10);
 INSERT INTO emp(EMPNO,ENAME,DEPTNO) values(2,'COTT',10)
*
ERROR at line 1:
ORA-00001: unique constraint (GYJ.PK_EMP) violated

 

总结：flashback table闪回表的同时也闪回了索引（此索引是建主键约束时产生的唯一索引，即也闪回了主键约束），但没有闪回外键约束。