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分类: Oracle

2008-03-31 13:03:53

来源:赛迪网    作者:Alice

有些时候我们在查询时不想通过lower或者upper等函数而把大小写的内容都查询出来,在Oracle 10g可以这么实现。

SQL> select * from v$version;

BANNER
----------------------------------------------------------------
Oracle Database 10g Enterprise Edition Release 10.2.0.1.0 - Prod
PL/SQL Release 10.2.0.1.0 - Production
CORE 10.2.0.1.0 Production

TNS for 32-bit Windows: Version 10.2.0.1.0 - Production
NLSRTL Version 10.2.0.1.0 - Production

SQL> select * from test;

ID
--------------------
A
a

SQL> select * from test where id='a';

ID
--------------------
a

SQL> ALTER SESSION SET NLS_COMP=ANSI;

Session altered

SQL> ALTER SESSION SET NLS_SORT=binary_ci;

Session altered

SQL> select * from test where id='A';

ID
--------------------
A
a

SQL> select * from test where id='a';

ID
--------------------
A
a

SQL>

10gR2中,nls_com新增加了一个值LINGUISTIC ,设置这个值,可以使在nl_sort中设置大小写不敏感。相应的,nl_sort也增加了一个值:BINARY_CI,(CI即Case Insensitive),也就是大小写不敏感。

但是,实际上设置过这两个值以后,并非真正大小写不敏感了,而是相当于Oracle会自动给语句加上upper函数。例子:

SQL> set autot on
SQL> select * from t2 where f1 = 'a';

F1 AAA
---------- ----------
a 2


Execution Plan
----------------------------------------------------------
Plan hash value: 2238318762

--------------------------------------------------------------------------------
-------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Tim
e |
--------------------------------------------------------------------------------
-------
| 0 | SELECT STATEMENT | | 1 | 5 | 2 (0)| 00:
00:01 |
| 1 | TABLE ACCESS BY INDEX ROWID| T2 | 1 | 5 | 2 (0)| 00:
00:01 |
|* 2 | INDEX RANGE SCAN | T2_IDX1 | 1 | | 1 (0)| 00:
00:01 |
--------------------------------------------------------------------------------
-------

Predicate Information (identified by operation id):
---------------------------------------------------

2 - access("F1"='a')


Statistics
----------------------------------------------------------
0 recursive calls
0 db block gets
0 consistent gets
0 physical reads
0 redo size
0 bytes sent via SQL*Net to client
0 bytes received via SQL*Net from client
0 SQL*Net roundtrips to/from client
0 sorts (memory)
0 sorts (disk)
1 rows processed

SQL> alter session set NLS_SORT=BINARY_CI;

Session altered.

SQL> alter session set NLS_COMP=LINGUISTIC;

Session altered.

SQL> select * from t2 where f1 = 'a';

F1 AAA
---------- ----------
A 1
a 2


Execution Plan
----------------------------------------------------------
Plan hash value: 1513984157

--------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
--------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 1 | 5 | 3 (0)| 00:00:01 |
|* 1 | TABLE ACCESS FULL| T2 | 1 | 5 | 3 (0)| 00:00:01 |
--------------------------------------------------------------------------

Predicate Information (identified by operation id):
---------------------------------------------------

1 - filter(NLSSORT("F1",'nls_sort=''BINARY_CI''')=HEXTORAW('6100') )


Statistics
----------------------------------------------------------
0 recursive calls
0 db block gets
0 consistent gets
0 physical reads
0 redo size
0 bytes sent via SQL*Net to client
0 bytes received via SQL*Net from client
0 SQL*Net roundtrips to/from client
0 sorts (memory)
0 sorts (disk)
2 rows processed
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