[每日一题] OCP1z0-047 :2013-08-24 ? FLASHBACK―TABLE/PRIMARY

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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(4,3      ENAME VARCHAR2(10),4      JOB   VARCHAR2(9),5      MGR   NUMBER(4,6      HIREDATE DATE,7      SAL   NUMBER(7,2),8      COMM  NUMBER(7,9      DEPTNO NUMBER(2,10           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,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,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,'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,DROPTIME from recyclebin;  no rows selected  gyj@OCM> SELECT EMPNO,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,'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,'COTT',10); INSERT INTO emp(EMPNO,10) * ERROR at line 1: ORA-00001: unique constraint (GYJ.BIN$5LNox53oT0PgQ4rZqMD+/Q==$0) violated   gyj@OCM> INSERT INTO emp(EMPNO,DEPTNO) values(3,'ING',55);  1 row created.   gyj@OCM> SELECT EMPNO,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,'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 

gyj@OCM>  INSERT INTO emp(EMPNO,10);  INSERT INTO emp(EMPNO,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。

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