SQL> select * from test order by id;

ID MC
-------------------- ------------------------------------------------------------
A AAAAA
B BBBBB
a aaaaa
b bbbbb

执行计划
----------------------------------------------------------
Plan hash value: 2007178810

---------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
---------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 4 | 176 | 4 (25)| 00:00:01 |
| 1 | SORT ORDER BY | | 4 | 176 | 4 (25)| 00:00:01 |
| 2 | TABLE ACCESS FULL| TEST | 4 | 176 | 3 (0)| 00:00:01 |
---------------------------------------------------------------------------

Note
-----
- dynamic sampling used for this statement

统计信息
----------------------------------------------------------
48 recursive calls
0 db block gets
19 consistent gets
0 physical reads
0 redo size
529 bytes sent via SQL*Net to client
385 bytes received via SQL*Net from client
2 SQL*Net roundtrips to/from client
1 sorts (memory)
0 sorts (disk)
4 rows processed

SQL> ALTER SESSION SET NLS_SORT=generic_m_ci;

会话已更改。

SQL> select * from test order by id;

ID MC
-------------------- ------------------------------------------------------------
A AAAAA
a aaaaa
B BBBBB
b bbbbb

执行计划
----------------------------------------------------------
Plan hash value: 2007178810

---------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
---------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 4 | 176 | 4 (25)| 00:00:01 |
| 1 | SORT ORDER BY | | 4 | 176 | 4 (25)| 00:00:01 |
| 2 | TABLE ACCESS FULL| TEST | 4 | 176 | 3 (0)| 00:00:01 |
---------------------------------------------------------------------------

Note
-----
- dynamic sampling used for this statement

统计信息
----------------------------------------------------------
4 recursive calls
0 db block gets
15 consistent gets
0 physical reads
0 redo size
529 bytes sent via SQL*Net to client
385 bytes received via SQL*Net from client
2 SQL*Net roundtrips to/from client
1 sorts (memory)
0 sorts (disk)
4 rows processed

如果设置session的环境不方便，以可以设置语句级的排序

代码:

SQL> select * from test order by id;

ID                   MC
-------------------- ------------------------------------------------------------
A                    AAAAA
B                    BBBBB
a                    aaaaa
b                    bbbbb

SQL> select * from test order by nlssort(id, 'nls_sort=generic_m_ci');

ID                   MC
-------------------- ------------------------------------------------------------
A                    AAAAA
a                    aaaaa
B                    BBBBB
b                    bbbbb