[20231013]CLOB型別的編碼問題.txt
[20231013]CLOB型別的編碼問題.txt
--//昨天想看一串unicode的內容,看了一些連結:
National Character Set(NLS_NCHAR_CHARACTERSET) defines the encoding of NCHAR, NVARCHAR2, and NCLOB columns and is in 9i
and up consistently Unicode. eg. AL16UTF16
國家字符集(NLS_NCHAR_CHARACTERSET)定義了NCHAR、NVARCHAR2和NCLOB列的編碼,並在9i中表示和一致的統一碼。例如AL16UTF16
Character Set(NLS_CHARACTERSET) defines the encoding of CHAR, VARCHAR2, LONG, and CLOB columns, these can also be used
for storing Unicode. eg AL32UTF8 or UTF8
字符集(NLS_CHARACTERSET)定義了CHAR、VARCHAR2、LONG和CLOB列的編碼,也可以使用它們用於儲存Unicode。如AL32UTF8或UTF8
--//注:感覺這裡不對,clob列的編碼好像也是AL16UTF16.我給測試看看是否這樣的情況.
The national Character set (NLS_NCHAR_CHARACTERSET) is used for data stored in NCHAR, NVARCHAR2, and NCLOB datatypes and
is a character set that is defined in addition to the (standard) database character set (NLS_CHARACTERSET), which is
used for CHAR, VARCHAR2, LONG and CLOB datatypes.
國家字符集(NLS_NCHAR_CHARACTERSET)用於儲存在NCHAR、NVARCHAR2和NCLOB資料型別和中的資料,和是在(標準)資料庫字符集
(NLS_CHARACTERSET)之外定義的字符集,即用於CHAR、VARCHAR2、LONG和CLOB資料型別。
1.環境:
$ env | grep NLS
NLS_LANG=AMERICAN_AMERICA.ZHS16GBK
NLS_TIME_TZ_FORMATx=HH24.MI.SSXFF TZH:TZM
NLS_TIMESTAMP_TZ_FORMAT=YYYY-MM-DD HH24:MI:SS.FF TZH:TZM
NLS_TIMESTAMP_FORMAT=YYYY-MM-DD HH24:MI:SS.FF
NLS_DATE_FORMAT=YYYY-MM-DD HH24:MI:SS
SCOTT@book> @ ver1
PORT_STRING VERSION BANNER
------------------------------ -------------- --------------------------------------------------------------------------------
x86_64/Linux 2.4.xx 11.2.0.4.0 Oracle Database 11g Enterprise Edition Release 11.2.0.4.0 - 64bit Production
SCOTT@book> select parameter,value from NLS_DATABASE_PARAMETERS where parameter in ('NLS_CHARACTERSET','NLS_NCHAR_CHARACTERSET');
PARAMETER VALUE
---------------------- ----------
NLS_CHARACTERSET ZHS16GBK
NLS_NCHAR_CHARACTERSET AL16UTF16
2.測試:
SCOTT@book> CREATE TABLE t1 ( id number,vc varchar2(30),nc nvarchar2(30),cc clob);
Table created.
SCOTT@book> insert into t1 values(1,'a測試中文a','a測試中文b','a測試中文c');
1 row created.
SCOTT@book> commit ;
Commit complete.
SCOTT@book> alter system checkpoint;
System altered.
SCOTT@book> select rowid from t1;
ROWID
------------------
AAAWsoAAEAAAAKvAAB
SCOTT@book> @ rowid AAAWsoAAEAAAAKvAAB
OBJECT FILE BLOCK ROW ROWID_DBA DBA TEXT
---------- ---------- ---------- ---------- -------------------- -------------------- ----------------------------------------
92968 4 687 1 0x10002AF 4,687 alter system dump datafile 4 block 687 ;
SCOTT@book> alter system dump datafile 4 block 687 ;
System altered.
3.檢查跟蹤檔案:
Block header dump: 0x010002af
Object id on Block? Y
seg/obj: 0x16b28 csc: 0x03.1873920b itc: 2 flg: E typ: 1 - DATA
brn: 0 bdba: 0x10002a8 ver: 0x01 opc: 0
inc: 0 exflg: 0
Itl Xid Uba Flag Lck Scn/Fsc
0x01 0x000a.004.0000d5b4 0x00c00bf1.2efa.1e --U- 1 fsc 0x0000.18739220
0x02 0x000a.00e.0000d5dd 0x00c00bf1.2efa.1d --U- 1 fsc 0x0043.1873920d
bdba: 0x010002af
data_block_dump,data header at 0x7fe7c95a4264
===============
tsiz: 0x1f98
hsiz: 0x16
pbl: 0x7fe7c95a4264
76543210
flag=--------
ntab=1
nrow=2
frre=-1
fsbo=0x16
fseo=0x1f04
avsp=0x1eee
tosp=0x1f33
0xe:pti[0] nrow=2 offs=0
0x12:pri[0] offs=0x1f53
0x14:pri[1] offs=0x1f04
block_row_dump:
tab 0, row 0, @0x1f53
tl: 2 fb: --HDFL-- lb: 0x2
tab 0, row 1, @0x1f04
tl: 79 fb: --H-FL-- lb: 0x1 cc: 4
col 0: [ 2] c1 02
col 1: [10] 61 b2 e2 ca d4 d6 d0 ce c4 61
col 2: [12] 00 61 6d 4b 8b d5 4e 2d 65 87 00 62
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
col 3: [48]
00 54 00 01 02 0c 80 00 00 02 00 00 00 01 00 00 06 72 79 80 00 1c 09 00 00
00 00 00 00 0c 00 00 00 00 00 01 00 61 6d 4b 8b d5 4e 2d 65 87 00 63
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
LOB
Locator:
Length: 84(48)
Version: 1
Byte Length: 2
LobID: 00.00.00.01.00.00.06.72.79.80
Flags[ 0x02 0x0c 0x80 0x00 ]:
Type: CLOB
Storage: BasicFile
Enable Storage in Row
Characterset Format: IMPLICIT
Partitioned Table: No
Options: VaringWidthReadWrite
Inode:
Size: 28
Flag: 0x09 [ Valid DataInRow ]
Future: 0x00 (should be '0x00')
Blocks: 0
Bytes: 12
Version: 00000.0000000001
Inline data[12]
Dump of memory from 0x00007FE7C95A61AB to 0x00007FE7C95A61B7
--//61 b2 e2 ca d4 d6 d0 ce c4 61 = a測試中文a , varchar2能對上.
--//注意看下劃線可以發現nvarchar2,clob的編碼一樣的.都是unicode big endian編碼.
$ echo fffe 00 61 6d 4b 8b d5 4e 2d 65 87 00 63 | xxd -r -p > a.txt
$ file a.txt
a.txt: Big-endian UTF-16 Unicode character data, with no line terminators
--//再上傳到windows的機器,使用記事本開啟就可以驗證編碼就是Big-endian UTF-16 Unicode character data.
--//我有點無法理解,intel系列機器不是採用Little endian嗎,為什麼nvarchar2,COLB使用的卻是Big endian.
SCOTT@book> select * from V$TRANSPORTABLE_PLATFORM;
PLATFORM_ID PLATFORM_NAME ENDIAN_FORMAT
----------- --------------------------------- --------------
1 Solaris[tm] OE (32-bit) Big
2 Solaris[tm] OE (64-bit) Big
7 Microsoft Windows IA (32-bit) Little
10 Linux IA (32-bit) Little
6 AIX-Based Systems (64-bit) Big
3 HP-UX (64-bit) Big
5 HP Tru64 UNIX Little
4 HP-UX IA (64-bit) Big
11 Linux IA (64-bit) Little
15 HP Open VMS Little
8 Microsoft Windows IA (64-bit) Little
9 IBM zSeries Based Linux Big
13 Linux x86 64-bit Little
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
16 Apple Mac OS Big
12 Microsoft Windows x86 64-bit Little
17 Solaris Operating System (x86) Little
18 IBM Power Based Linux Big
19 HP IA Open VMS Little
20 Solaris Operating System (x86-64) Little
21 Apple Mac OS (x86-64) Little
20 rows selected.
來自 “ ITPUB部落格 ” ,連結:http://blog.itpub.net/267265/viewspace-2989216/,如需轉載,請註明出處,否則將追究法律責任。
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