nls_sort和nlssort 排序功能介绍

ALTER SESSION SET NLS_SORT=''; 排序影响整个会话
Oracle9i之前，中文是按照二进制编码进行排序的。  
   
  　　在oracle9i中新增了按照拼音、部首、笔画排序功能。设置NLS_SORT值    
   
  　　SCHINESE_RADICAL_M   按照部首（第一顺序）、笔划（第二顺序）排序    
   
  　　SCHINESE_STROKE_M   按照笔划（第一顺序）、部首（第二顺序）排序    
   
  　　SCHINESE_PINYIN_M   按照拼音排序
oracle9i中新增了按照拼音、部首、笔画排序功能
拼音 SELECT * FROM TEAM ORDER BY NLSSORT(列名,'NLS_SORT = SCHINESE_PINYIN_M')
笔划 SELECT * FROM TEAM ORDER BY NLSSORT(列名,'NLS_SORT = SCHINESE_STROKE_M')
部首 SELECT * FROM TEAM ORDER BY NLSSORT(列名,'NLS_SORT = SCHINESE_RADICAL_M')




Oracle9i之前，中文是按照二进制编码进行排序的。在oracle9i中新增了按照拼音、部首、笔画排序功能。
1、设置NLS_SORT参数值
      SCHINESE_RADICAL_M 按照部首（第一顺序）、笔划（第二顺序）排序
      SCHINESE_STROKE_M 按照笔划（第一顺序）、部首（第二顺序）排序
      SCHINESE_PINYIN_M 按照拼音排序
2、Session级别的设置，修改ORACLE字段的默认排序方式：
      按拼音：alter session set nls_sort = SCHINESE_PINYIN_M;
      按笔画：alter session set nls_sort = SCHINESE_STROKE_M;
      按偏旁：alter session set nls_sort = NLS_SORT=SCHINESE_RADICAL_M；
3、语句级别设置排序方式：
      按照笔划排序
      select * from dept order by nlssort(name,'NLS_SORT=SCHINESE_STROKE_M');
      按照部首排序
      select * from dept order by nlssort(name,'NLS_SORT=SCHINESE_RADICAL_M');
      按照拼音排序，此为系统的默认排序方式
      select * from dept order by nlssort(name,'NLS_SORT=SCHINESE_PINYIN_M');
4、修改系统参数（数据库所在操作系统）：
      set NLS_SORT=SCHINESE_RADICAL_M ;
       export NLS_SORT （sh）
       setenv NLS_SORT SCHINESE_RADICAL_M (csh)
      HKLC\SOFTWARE\ORACLE\home0\NLS_SORT (win注册表)


Oracle 官方说明

NLS_SORT NLS_SORT specifies the collating sequence for ORDER BY queries. NLS_COMPNLS_COMP specifies the collation behavior of the database session.


Property
Description
Parameter type
String
Syntax
NLS_SORT = { BINARY | linguistic_definition }
Default value
Derived from NLS_LANGUAGE
Modifiable
ALTER SESSION
Range of values
BINARY or any valid linguistic definition name


If the value is BINARY, then the collating sequence for ORDER BY queries is based on the numeric value of characters (a binary sort that requires less system overhead).
If the value is a named linguistic sort, sorting is based on the order of the defined linguistic sort. Most (but not all) languages supported by the NLS_LANGUAGE parameter also support a linguistic sort with the same name.
Note:
Setting NLS_SORT to anything other than BINARY causes a sort to use a full table scan, regardless of the path chosen by the optimizer. BINARY is the exception because indexes are built according to a binary order of keys. Thus the optimizer can use an index to satisfy the ORDER BY clause when NLS_SORT is set to BINARY. If NLS_SORT is set to any linguistic sort, the optimizer must include a full table scan and a full sort in the execution plan.
         You must use the NLS_SORT operator with comparison operations if you want the linguistic sort behavior.


Property
Description
Parameter type
String
Syntax
NLS_COMP = { BINARY | LINGUISTIC | ANSI }
Default value
BINARY
Modifiable
ALTER SESSION
Basic
No

Values:
BINARY
Normally, comparisons in the WHERE clause and in PL/SQL blocks is binary unless you specify the NLSSORT function.
LINGUISTIC
Comparisons for all SQL operations in the WHERE clause and in PL/SQL blocks should use the linguistic sort specified in the NLS_SORT parameter. To improve the performance, you can also define a linguistic index on the column for which you want linguistic comparisons.
ANSI
A setting of ANSI is for backwards compatibility; in general, you should set NLS_COMP to LINGUISTIC

注意：当使用了NLS_SORT或NLS_COMP，应该指定函数索引来提高数据库性能。如
create index [schema.]indexName on tableName(function(propertyName))

注意：虽然能在oracle查询的时候能用得上，但不知道为什么，当映射到hibernate上时却无效，依然按NLS_SORT=binary排序，不过可以使用@org.hibernate.annotation.OrderBy("nlssort(name,'NLS_SORT=SCHINESE_PINYIN_M')")指定排序方法