OCP-1Z0-新051-61题版本-1

QUESTION NO: 1

Evaluate the SQL statement:

TRUNCATE TABLE DEPT;

Which three are true about the SQL statement? (Choose three.)

A. It releases the storage space used by the table.

B. It does not release the storage space used by the table.

C. You can roll back the deletion of rows after the statement executes.

D. You can NOT roll back the deletion of rows after the statement executes.

E. An attempt to use DESCRIBE on the DEPT table after the TRUNCATE statement executes will display an error.

F. You must be the owner of the table or have DELETE ANY TABLE system privileges to truncate the DEPT table

Answer: A,D,F

答案解析：

参考：http://docs.oracle.com/cd/E11882_01/server.112/e25494/general.htm#ADMIN11534

It is a DDL statement and cannot be rolled back D正确，C错误

A

TRUNCATE

statement also specifies whether space currently allocated
for the table is returned to the containing tablespace after truncation. A正确。B错误

You can truncate any table or cluster in your own schema. Any user who has the

DROP ANY TABLE

system privilege can truncate a table or cluster in any schema. F正确。

sys@TESTDB>conn scott/tiger

Connected.

scott@TESTDB>select * from dept_new

2 ;

DEPTNO DNAME LOC

---------- -------------- -------------

10 ACCOUNTING NEW YORK

20 RESEARCH DALLAS

30 SALES CHICAGO

40 OPERATIONS BOSTON

50 IT CHINA

60 CLERK BEIJING

6 rows selected.

scott@TESTDB>TRUNCATE TABLE dept_new;

Table truncated.

scott@TESTDB>select * from dept_new;

no rows selected

scott@TESTDB>desc dept_new; desc不会报错。E错误。

Name Null? Type

------------------------------------------------------------- - -------- ------------------------------

DEPTNO NUMBER(2)

DNAME VARCHAR2(14)

LOC VARCHAR2(13)

scott@TESTDB>rollback; --不能rollback

Rollback complete.

scott@TESTDB>select * from dept_new; --没有返回

no rows selected

Using TRUNCATE

You can delete all rows of the table using the

TRUNCATE

statement.
For example, the following statement truncates the

emp

table:
TRUNCATE TABLE emp;
Using the

TRUNCATE

statement provides a fast, efficient method for deleting all rows from a table or cluster. A

TRUNCATE

statement does not generate any undo information and it commits immediately. It
is a DDL statement and cannot be rolled back. A

TRUNCATE

statement does not affect any structures associated with the table being truncated (constraints
and triggers) or authorizations. A

TRUNCATE

statement also specifies whether space currently allocated for the table is returned to the containing tablespace after truncation.

You can truncate any table or cluster in your own schema. Any user who has the

DROP ANY TABLE

system privilege can
truncate a table or cluster in any schema.

Before truncating a table or clustered table containing a parent key, all referencing foreign keys in different tables must be disabled. A self-referential constraint does not have to be disabled.
As a

TRUNCATE

statement deletes rows from a table, triggers associated with the table are not fired. Also, a

TRUNCATE

statement does not generate any audit information corresponding to

DELETE

statements
if auditing is enabled. Instead, a single audit record is generated for the

TRUNCATE

statement being issued.
A hash cluster cannot be truncated, nor can tables within a hash or index cluster be individually truncated. Truncation of an index cluster deletes all rows from all tables in the cluster. If all the rows must be deleted from
an individual clustered table, use the

DELETE

statement or drop and re-create the table.
The

TRUNCATE

statement has several options
that control whether space currently allocated for a table or cluster is returned to the containing tablespace after truncation.
These options also apply to any associated indexes. When a table or cluster is truncated, all associated indexes are also truncated. The storage parameters for a truncated table, cluster, or associated indexes are not changed
as a result of the truncation.
These

TRUNCATE

options are:

DROP STORAGE

, the default option, reduces the number of extents allocated to the resulting table to the original setting for

MINEXTENTS

. Freed extents are then returned to the system and can be used by other objects.

DROP

ALL

STORAGE

drops the segment. In addition to the

TRUNCATE

TABLE

statement,

DROP

ALL

STORAGE

also applies to the

ALTER

TABLE

TRUNCATE

(SUB)PARTITION

statement.
This option also drops any dependent object segments associated with the partition being truncated.

DROP

ALL

STORAGE

is not supported for clusters.

Note:

This functionality is available with Oracle Database 11g release 2 (11.2.0.2).
TRUNCATE TABLE emp DROP ALL STORAGE;

REUSE STORAGE

specifies that all space currently allocated for the table or cluster remains allocated to it. For example, the following statement truncates the

emp_dept

cluster, leaving all extents previously allocated for the cluster
available for subsequent inserts and deletes:

TRUNCATE CLUSTER emp_dept REUSE STORAGE;