Oracle教程之管理表（二）--Oracle管理普通表
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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