达梦dba_segments指定表名查询到的大小都包含哪些数据

一、结论

dba_segments指定表名查询到的段大小包含索引、约束、表字段数据（包含LOB字段）
（1）表（不包含LOB字段）创建默认分配2个簇，1个簇用于存放表结构及字段数据，1个簇用于存放cluster类型的索引
（2）创建索引默认会分配2个簇，用于存放normal索引数据
（3）创建约束不会额外分配空间，除非是主键或唯一约束
（4）添加LOB字段默认分配2个簇，用于存放lob字段数据
（5）表（包含LOB字段）创建默认分配4个簇，1个簇用于存放表结构及字段数据，1个簇用于存放cluster类型的索引，2和簇用于存放lob字段数据
二、测试过程

（一）创建测试表，查看初始大小

1. create table test01(id number,name varchar2(10));
3. SQL> select owner,segment_name,bytes,blocks,extents,initial_extent from dba_segments where owner='SYSDBA' and segment_name='TEST01';
5. OWNER  SEGMENT_NAME BYTES                BLOCKS               EXTENTS              INITIAL_EXTENT      
6. ------ ------------ -------------------- -------------------- -------------------- --------------------
7. SYSDBA TEST01       2097152              64                   2                    1048576
9. SQL> select owner,index_name,index_type,initial_extent from dba_indexes where owner='SYSDBA' and table_name='TEST01';
11. OWNER  INDEX_NAME    INDEX_TYPE INITIAL_EXTENT
12. ------ ------------- ---------- --------------
13. SYSDBA INDEX33566761 CLUSTER    1
15. SQL> select owner,segment_name,bytes,blocks,extents,initial_extent from dba_segments where owner='SYSDBA' and segment_name in('INDEX33566761');
16. 未选定行

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（二）添加索引，查看空间变化

1. create index idx_test01_name on test01(name);
3. SQL> select owner,segment_name,bytes,blocks,extents,initial_extent from dba_segments where owner='SYSDBA' and segment_name='TEST01';
5. OWNER SEGMENT_NAME BYTES BLOCKS EXTENTS INITIAL_EXTENT
6. ------ ------------ -------------------- -------------------- -------------------- --------------------
7. SYSDBA TEST01 4194304 128 4 1048576
9. SQL> select owner,index_name,index_type,initial_extent from dba_indexes where owner='SYSDBA' and table_name='TEST01';
11. OWNER INDEX_NAME INDEX_TYPE INITIAL_EXTENT
12. ------ --------------- ---------- --------------
13. SYSDBA INDEX33566761 CLUSTER 1
14. SYSDBA IDX_TEST01_NAME NORMAL 1
16. SQL> select owner,segment_name,bytes,blocks,extents,initial_extent from dba_segments where owner='SYSDBA' and segment_name in('INDEX33566761','IDX_TEST01_NAME');
18. OWNER SEGMENT_NAME BYTES BLOCKS EXTENTS INITIAL_EXTENT
19. ------ --------------- -------------------- -------------------- -------------------- --------------------
20. SYSDBA IDX_TEST01_NAME 2097152 64 2 1048576

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（三）添加主键，查看空间变化

1. alter table test01 add constraint pk_test01_id primary key(id);
3. SQL> select owner,segment_name,bytes,blocks,extents,initial_extent from dba_segments where owner='SYSDBA' and segment_name='TEST01';
5. OWNER SEGMENT_NAME BYTES BLOCKS EXTENTS INITIAL_EXTENT
6. ------ ------------ -------------------- -------------------- -------------------- --------------------
7. SYSDBA TEST01 6291456 192 6 1048576
9. SQL> select owner,index_name,index_type,initial_extent from dba_indexes where owner='SYSDBA' and table_name='TEST01';
11. OWNER INDEX_NAME INDEX_TYPE INITIAL_EXTENT
12. ------ --------------- ---------- --------------
13. SYSDBA INDEX33566761 CLUSTER 1
14. SYSDBA INDEX33566763 NORMAL 1
15. SYSDBA IDX_TEST01_NAME NORMAL 1
17. SQL> select constraint_name,constraint_type,status,index_name from dba_constraints where owner='SYSDBA' and table_name='TEST01';
19. CONSTRAINT_NAME CONSTRAINT_TYPE STATUS INDEX_NAME
20. --------------- --------------- ------- -------------
21. PK_TEST01_ID P ENABLED INDEX33566763
23. SQL> select owner,segment_name,bytes,blocks,extents,initial_extent from dba_segments where owner='SYSDBA' and segment_name in('INDEX33566761','IDX_TEST01_NAME','INDEX33566763');
25. OWNER SEGMENT_NAME BYTES BLOCKS EXTENTS INITIAL_EXTENT
26. ------ --------------- -------------------- -------------------- -------------------- --------------------
27. SYSDBA IDX_TEST01_NAME 2097152 64 2 1048576
28. SYSDBA INDEX33566763 2097152 64 2 1048576

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（四）创建约束，查看空间变化

1. alter table test01 add constraint ck_test01_id check(id>=1);
3. SQL> select owner,segment_name,bytes,blocks,extents,initial_extent from dba_segments where owner='SYSDBA' and segment_name='TEST01';
5. OWNER SEGMENT_NAME BYTES BLOCKS EXTENTS INITIAL_EXTENT
6. ------ ------------ -------------------- -------------------- -------------------- --------------------
7. SYSDBA TEST01 6291456 192 6 1048576
9. SQL> select constraint_name,constraint_type,status,index_name from dba_constraints where owner='SYSDBA' and table_name='TEST01';
11. CONSTRAINT_NAME CONSTRAINT_TYPE STATUS INDEX_NAME
12. --------------- --------------- ------- -------------
13. CK_TEST01_ID C ENABLED NULL
14. PK_TEST01_ID P ENABLED INDEX33566763

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（五）增加lob列和普通列，查看空间变化

1. alter table test01 add content clob;
3. SQL> select owner,segment_name,bytes,blocks,extents,initial_extent from dba_segments where owner='SYSDBA' and segment_name='TEST01';
5. OWNER SEGMENT_NAME BYTES BLOCKS EXTENTS INITIAL_EXTENT
6. ------ ------------ -------------------- -------------------- -------------------- --------------------
7. SYSDBA TEST01 8388608 256 8 1048576
9. alter table test01 add city varchar2(10);
11. SQL> select owner,segment_name,bytes,blocks,extents,initial_extent from dba_segments where owner='SYSDBA' and segment_name='TEST01';
13. OWNER SEGMENT_NAME BYTES BLOCKS EXTENTS INITIAL_EXTENT
14. ------ ------------ -------------------- -------------------- -------------------- --------------------
15. SYSDBA TEST01 8388608 256 8 1048576
18. SQL> select id,name,crtdate from sysobjects where name='TEST01' and schid in(select id from sysobjects where name='SYSDBA' and type$='SCH');
20. ID NAME CRTDATE
21. ----------- ------ --------------------------
22. 5751 TEST01 2022-02-22 14:55:03.347000
24. SQL> SELECT TABLE_USED_LOB_PAGES('SYSDBA','TEST01');
26. TABLE_USED_LOB_PAGES('SYSDBA','TEST01')
27. ---------------------------------------
28. 6 ---这个返回的是数据块，2个簇实际在用的数据块数量只有6个

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（六）创建包含LOB字段的表

1. SQL> create table test02(id number,name varchar2(10),content clob);
2. SQL> select owner,segment_name,bytes,blocks,extents,initial_extent from dba_segments where owner='SYSDBA' and segment_name='TEST02';
4. OWNER SEGMENT_NAME BYTES BLOCKS EXTENTS INITIAL_EXTENT
5. ------ ------------ -------------------- -------------------- -------------------- --------------------
6. SYSDBA TEST02 4194304 128 4 1048576

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出处：https://www.cnblogs.com/huzei/
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