oracle 設定 大小寫 敏感

（以下內容只有在"="號的情況下生效，LIKE 不行。）

有時候我們查詢的時候不想通過lower或者upper等函數而把大小寫內容都查詢出來，如從sqlserver、mysql等轉移到
oracle時。在oracle10g可以通過修改session來實現:

ALTER SESSION SET NLS_COMP=ANSI;

ALTER SESSION SET NLS_SORT=binary_ci;

解析:

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新增加了一個值LINGUISTIC
，設定這個值，可以使在nl_sort中設定大小寫不敏感。相應的，nl_sort也增加了一個值：BINARY_CI，(CI即Case
Insensitive)，也就是大小寫不敏感。

但是，實際上設定過這兩個值以後，並非真正大小寫不敏感了，而是相當於Oracle會自動給語句加上upper函數。看以下例子：

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):
----------