Oracle教程之管理表（二）--Oracle管理普通表

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Oracle小混子 2013-04-02 09:32:57 ©著作权

文章标签 Oracle Oracle管理表 Oracle管理普通表 Oracle普通表管理 文章分类 Oracle 数据库

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1、建立普通表

02:25:59 SQL> create table deparment(

02:26:52 2 deptno number(4),dname varchar2(20),loc varchar2(12))

02:27:22 3 pctfree 20 pctused 50 tablespace users01

02:27:45 4 storage(minextents 3);

Table created.

02:28:19 SQL> alter table deparment rename to department;

Table altered.

02:28:52 SQL> desc department;

Name Null? Type

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

DEPTNO NUMBER(4)

DNAME VARCHAR2(20)

LOC VARCHAR2(12)

02:30:13 SQL> select tablespace_name,extents,bytes from user_segments

02:30:31 2 where segment_name='DEPARTMENT';

TABLESPACE_NAME EXTENTS BYTES

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

USERS01 3 393216

02:30:47 SQL>

查看EMP1表段信息：

22:59:29 SQL> COL SEGMENT_NAME FOR A20

22:59:40 SQL> R

1 select SEGMENT_NAME,SEGMENT_TYPE,BLOCKS,EXTENTS,INITIAL_EXTENT ,TABLESPACE_NAME from user_segments

2* where segment_name='EMP1'

SEGMENT_NAME SEGMENT_TYPE BLOCKS EXTENTS INITIAL_EXTENT TABLESPACE_NAME

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

EMP1 TABLE 8 1 65536 USERS

23:00:31 SQL> SELECT TABLE_NAME,BLOCKS,NUM_ROWS,EMPTY_BLOCKS FROM USER_TABLES

23:01:31 2 WHERE TABLE_NAME='EMP1';

TABLE_NAME BLOCKS NUM_ROWS EMPTY_BLOCKS

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

EMP1 4 13 0

23:01:40 SQL> ANALYZE TABLE EMP1 COMPUTE STATISTICS;

Table analyzed.

23:02:36 SQL> SELECT TABLE_NAME,BLOCKS,NUM_ROWS,EMPTY_BLOCKS FROM USER_TABLES

23:02:39 2 WHERE TABLE_NAME='EMP1';

TABLE_NAME BLOCKS NUM_ROWS EMPTY_BLOCKS

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

EMP1 4 13 4

23:02:42 SQL> DELETE FROM EMP1;

13 rows deleted.

23:03:30 SQL> ANALYZE TABLE EMP1 COMPUTE STATISTICS;

Table analyzed.

23:03:35 SQL> SELECT TABLE_NAME,BLOCKS,NUM_ROWS,EMPTY_BLOCKS FROM USER_TABLES

23:03:39 2 WHERE TABLE_NAME='EMP1';

TABLE_NAME BLOCKS NUM_ROWS EMPTY_BLOCKS

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

EMP1 4 0 4

23:03:43 SQL> TRUNCATE TABLE EMP1;

Table truncated.

23:04:37 SQL> ANALYZE TABLE EMP1 COMPUTE STATISTICS;

Table analyzed.

23:04:44 SQL> SELECT TABLE_NAME,BLOCKS,NUM_ROWS,EMPTY_BLOCKS FROM USER_TABLES

23:04:47 2 WHERE TABLE_NAME='EMP1';

TABLE_NAME BLOCKS NUM_ROWS EMPTY_BLOCKS

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

EMP1 0 0 8

23:05:29 SQL> SELECT SEGMENT_NAME ,EXTENT_ID,BLOCKS FROM USER_EXTENTS

23:06:01 2 WHERE SEGMENT_NAME='EMP1';

SEGMENT_NAME EXTENT_ID BLOCKS

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

EMP1 0 8

2、修改表的物理结构

02:52:49 SQL> alter table department

02:52:56 2 pctfree 40 pctused 35 initrans 3;

Table altered.

00:10:38 SQL> create table emp3(id int,name varchar2(10))

00:10:50 2 PCTFREE 20

00:11:07 3 PCTUSED 40

00:11:23 4 STORAGE(

00:11:27 5 NEXT 200K

00:11:30 6 MINEXTENTS 2

00:11:37 7 MAXEXTENTS 10);

Table created.

Emp3 默认表空间为users ，其表空间管理方式local，没有定义initial 参数，其初始化extent大小为64k

00:11:40 SQL> select segment_name,blocks,extents,initial_extent,next_extent,MIN_EXTENTS,MAX_EXTENTS from user_segments

00:11:50 2 where segment_name='EMP3';

SEGMENT_NAME BLOCKS EXTENTS INITIAL_EXTENT NEXT_EXTENT MIN_EXTENTS MAX_EXTENTS

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

EMP3 40 5 270336 1 2147483645

00:12:02 SQL> select segment_name,blocks,extents,initial_extent/1024,next_extent,MIN_EXTENTS,MAX_EXTENTS from user_segments

00:13:23 2 where segment_name='EMP3';

SEGMENT_NAME BLOCKS EXTENTS INITIAL_EXTENT/1024 NEXT_EXTENT MIN_EXTENTS MAX_EXTENTS

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

EMP3 40 5 264 1 2147483645

INITIAL_EXTENT=64 + 200 k ，初始化extent 为64，next extent 200，最少分配两个区（minextents=2）；

3、重新组织表

02:55:06 SQL> alter table department move tablespace users01;

Table altered

重新组织表后，原来的索引会无效，必须重建索引。

4、手工分配和释放表空间

02:59:18 SQL> COL FILE_NAME FOR A30

02:59:29 SQL> R

1* select * from dba_data_files where tablespace_name like 'USERS01'

FILE_NAME FILE_ID TABLESPACE_NAME BYTES BLOCKS STATUS RELATIVE_FNO AUT MAXBYTES MAXBLOCKS INCREMENT_BY USER_BYTES USER_BLOCKS ONLINE_

------------------------------ ---------- ------------------------------ ---------- ---------- --------- ------------ --- ---------- --------/disk1/oradata/orcl/user01.dbf 6 USERS01 10485760 1280 AVAILABLE 6 NO 0 0 0 10354688 1264 ONLINE

03:02:12 SQL> alter table department allocate extent

03:02:31 2 (size 500k datafile '/disk1/oradata/orcl/user01.dbf');

Table altered.

03:03:00 SQL> alter table department deallocate unused keep 0;

Table altered.

默认情况下释放剩余空间后表段的区个数不会低于MINEXTENTS，而如果要释放minextents下的剩余空间，需要带有keept 0 的选项。

5、修改列定义

03:37:52 SQL> desc department;

Name Null? Type

----------------------------------------------------------------------------------------------------------------- -------- ----------------- DEPTNO NUMBER(2)

DNAME VARCHAR2(10)

03:38:02 SQL> alter table department add (loc varchar2(10));

Table altered.

03:38:33 SQL> alter table department modify loc varchar2(15);

Table altered.

需要注意：当缩减char类型列的长度时，如果该表中已经包含数据，就必须将初始化参数blank_trimming 设置为true

03:01:37 SQL> show parameter blank

NAME TYPE VALUE

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

blank_trimming boolean FALSE

03:41:00 SQL>

6、修改列名

03:40:49 SQL> alter table department rename column loc to loca;

Table altered.

03:42:59 SQL> desc department;

Name Null? Type

----------------------------------------------------------------------------------------------------------------- -------- ----------------- DEPTNO NUMBER(2)

DNAME VARCHAR2(10)

LOCA VARCHAR2(15)

修改列名会使视图、过程等相关对象转变为无效状态。

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