验证一个052考试题

8 、Examine the following statement:

SQL> ALTER TABLE SALES MODIFY CONSTRAINT pk DISABLE VALIDATE;

Which three statements are true?

A)Rows may be inserted into the table.

B) The PK index is made unusable.

C)The PK index is dropped.

D)The constraint is still enforced for updated rows.

E)The constraint is still enforced for inserted rows.

Answer:CDE

--=====================

SQL> create table tt(id int primary key) ;

表已创建。

SQL> desc dba_constraints
名称 是否为空? 类型
----------------------------------------- -------- ----------------------------
OWNER VARCHAR2(60)
CONSTRAINT_NAME NOT NULL VARCHAR2(30)
CONSTRAINT_TYPE VARCHAR2(1)
TABLE_NAME NOT NULL VARCHAR2(30)
SEARCH_CONDITION LONG
R_OWNER VARCHAR2(60)
R_CONSTRAINT_NAME VARCHAR2(30)
DELETE_RULE VARCHAR2(9)
STATUS VARCHAR2(8)
DEFERRABLE VARCHAR2(14)
DEFERRED VARCHAR2(9)
VALIDATED VARCHAR2(13)
GENERATED VARCHAR2(14)
BAD VARCHAR2(3)
RELY VARCHAR2(4)
LAST_CHANGE DATE
INDEX_OWNER VARCHAR2(30)
INDEX_NAME VARCHAR2(30)
INVALID VARCHAR2(7)
VIEW_RELATED VARCHAR2(14)

SQL> SELECT CONSTRAINT_NAME,CONSTRAINT_type from dba_constraints where table_name='TT';

CONSTRAINT_NAME C
------------------------------ -
SYS_C006993 P

SQL> alter table tt modify constraint SYS_C006993 disable validate;

表已更改。

SQL> SELECT CONSTRAINT_NAME,CONSTRAINT_type,status from dba_constraints where table_name='TT';

CONSTRAINT_NAME C STATUS
------------------------------ - --------
SYS_C006993 P DISABLED

SQL> SELECT CONSTRAINT_NAME,CONSTRAINT_type,status,validated from dba_constraints where table_name='TT';

CONSTRAINT_NAME C STATUS VALIDATED
------------------------------ - -------- -------------
SYS_C006993 P DISABLED VALIDATED

SQL> SELECT CONSTRAINT_NAME,CONSTRAINT_type,status,validated,index_name from dba_constraints where table_name='TT';

CONSTRAINT_NAME C STATUS VALIDATED
------------------------------ - -------- -------------
INDEX_NAME
------------------------------
SYS_C006993 P DISABLED VALIDATED

SQL> set linesize 120
SQL> SELECT CONSTRAINT_NAME,CONSTRAINT_type,status,validated,index_name from dba_constraints where table_name='TT';

CONSTRAINT_NAME C STATUS VALIDATED INDEX_NAME
------------------------------ - -------- ------------- ------------------------------
SYS_C006993 P DISABLED VALIDATED

SQL> select index_name from dba_indexes where table_name='TT';

未选定行

SQL> insert into tt values(1);
insert into tt values(1)
*
第 1 行出现错误:
ORA-25128: 不能对带有禁用和验证约束条件 (XYS.SYS_C006993) 的表进行插入/更新/删除

SQL>