Oracle嵌套表存储格式浅析

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  Oracle嵌套表很少用，下面来研究下其如何存储的。用一个例子，一个用户对应对个部门。

SQL> select * from v$version;
BANNER
--------------------------------------------------------------------------------
Oracle Database 11g Enterprise Edition Release 11.2.0.1.0 - 64bit Production
PL/SQL Release 11.2.0.1.0 - Production
CORE    11.2.0.1.0      Production
TNS for Linux: Version 11.2.0.1.0 - Production
NLSRTL Version 11.2.0.1.0 - Production

SQL> create type t_dept as object(

SQL> commit;

--要想遍历用户的所有部门信息，需要用table这种特殊的形式

DEPTS      SYS_LOB0000082685C00003$$      SYS_IL0000082685C00003$$

--再测试下跟普通的clob有什么区别

drop table test purge;
create table test
(
  id number,
  t_clob clob
);
insert into test values(1,‘开发一组开发二组‘);
insert into test values(1,‘设计一组设计二组‘);
insert into test values(1,‘家‘);

commit;

tab 0, row 0, @0x3f5d
tl: 59 fb: --H-FL-- lb: 0x1  cc: 2
col  0: [ 2]  c1 02
col  1: [52]
 00 54 00 01 02 0c 80 00 00 02 00 00 00 01 00 00 00 0a e4 4a 00 20 09 00 00
 00 00 00 00 10 00 00 00 00 00 01 5f 00 53 d1 4e 00 7e c4 5f 00 53 d1 4e 8c
 7e c4
LOB
Locator:
  Length:        84(52)
  Version:        1
  Byte Length:    2
  LobID: 00.00.00.01.00.00.00.0a.e4.4a
  Flags[ 0x02 0x0c 0x80 0x00 ]:
    Type: CLOB 
    Storage: BasicFile
    Enable Storage in Row 
    Characterset Format: IMPLICIT
    Partitioned Table: No
    Options: VaringWidthReadWrite 
  Inode: 
    Size:     32
    Flag:     0x09 [ Valid DataInRow ]
    Future:   0x00 (should be ‘0x00‘)
    Blocks:   0
    Bytes:    16
    Version:  00000.0000000001
    Inline data[16]
Dump of memory from 0x00002AE680C155EC to 0x00002AE680C155FC
2AE680C155E0                            D153005F              [_.S.]
2AE680C155F0 C47E004E D153005F C47E8C4E           [N.~._.S.N.~.]    
tab 0, row 1, @0x3f22
tl: 59 fb: --H-FL-- lb: 0x1  cc: 2
col  0: [ 2]  c1 02
col  1: [52]
 00 54 00 01 02 0c 80 00 00 02 00 00 00 01 00 00 00 0a e4 4b 00 20 09 00 00
 00 00 00 00 10 00 00 00 00 00 01 8b be 8b a1 4e 00 7e c4 8b be 8b a1 4e 8c
 7e c4
LOB
Locator:
  Length:        84(52)
  Version:        1
  Byte Length:    2
  LobID: 00.00.00.01.00.00.00.0a.e4.4b
  Flags[ 0x02 0x0c 0x80 0x00 ]:
    Type: CLOB 
    Storage: BasicFile
    Enable Storage in Row 
    Characterset Format: IMPLICIT
    Partitioned Table: No
    Options: VaringWidthReadWrite 
  Inode: 
    Size:     32
    Flag:     0x09 [ Valid DataInRow ]
    Future:   0x00 (should be ‘0x00‘)
    Blocks:   0
    Bytes:    16
    Version:  00000.0000000001
    Inline data[16]
Dump of memory from 0x00002AE680C155B1 to 0x00002AE680C155C1
2AE680C155B0 8BBE8B01 7E004EA1 8BBE8BC4 7E8C4EA1  [.....N.~.....N.~]
2AE680C155C0 02012CC4                             [.,..]            
tab 0, row 2, @0x3ef5
tl: 45 fb: --H-FL-- lb: 0x1  cc: 2
col  0: [ 2]  c1 02
col  1: [38]
 00 54 00 01 02 0c 80 00 00 02 00 00 00 01 00 00 00 0a e4 4c 00 12 09 00 00
 00 00 00 00 02 00 00 00 00 00 01 5b b6
LOB
Locator:
  Length:        84(38)
  Version:        1
  Byte Length:    2
  LobID: 00.00.00.01.00.00.00.0a.e4.4c
  Flags[ 0x02 0x0c 0x80 0x00 ]:
    Type: CLOB 
    Storage: BasicFile
    Enable Storage in Row 
    Characterset Format: IMPLICIT
    Partitioned Table: No
    Options: VaringWidthReadWrite 
  Inode: 
    Size:     18
    Flag:     0x09 [ Valid DataInRow ]
    Future:   0x00 (should be ‘0x00‘)
    Blocks:   0
    Bytes:    2
    Version:  00000.0000000001
    Inline data[2]

 选取两次的dump的内容，不过还是不能确定两者是否等价：

 00 01 00 00 00 00 00 01 00 00 00 0a e4 49 00 21 09 00 00 00 00 00 00 11 00
 00 00 00 00 01 88 01 11 01 01 00 01 09 84 01 09 02 c2 06 02 bc d2

 00 54 00 01 02 0c 80 00 00 02 00 00 00 01 00 00 00 0a e4 4c 00 12 09 00 00
 00 00 00 00 02 00 00 00 00 00 01 5b b6

   总结：嵌套是通过lob在存储嵌套的内容的，TOM说作为一种存储机制，他更倾向于创建父子表，可以再创建一个视图，看上去像一个真正的嵌套表一样，嵌套表适合于编程构造。

Oracle嵌套表存储格式浅析

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原文地址：http://blog.csdn.net/stevendbaguo/article/details/39184405