开发人员有个需求，需将一个字符串，转成nvarchar2类型。但是测试是乱码，例句如下：
SQL> select(selectutl_raw.cast_to_nvarchar2(utl_raw.cast_to_raw('i am nvarchar2string')) from dual) from dual;
(SELECTUTL_RAW.CAST_TO_NVARCHAR2(UTL_RAW.CAST_TO_RAW('IAMNVARCHAR2STRING'))FROMDUAL)
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??????????
cast_to_raw函数按照缺省字符集将varchar2字符串转换为RAW，而cast_to_nvarchar2是将RAW转换成Nvarchar2类型，nvarchar2依据所选的国家字符集。
SQL> col value formata22
SQL> select * from nls_database_parameters
2 where parameterin('NLS_NCHAR_CHARACTERSET','NLS_CHARACTERSET');
PARAMETER VALUE
------------------------------ ----------------------
NLS_NCHAR_CHARACTERSET AL16UTF16
NLS_CHARACTERSET ZHS16GBK
数据库缺省字符集ZHS16GBK，而国家字符集为AL16UTF16，将ZHS16GBK的RAW用AL16UTF16显示，会产生乱码。如果不产生乱码可以将原字符串'iam nvarchar2 string'转换国家字符集，输出类型为NVARCHAR2。
SQL> select (selectutl_raw.cast_to_nvarchar2(utl_raw.cast_to_raw(translate('i amnvarchar2 string' using nchar_cs))) from dual) from dual;
(SELECTUTL_RAW.CAST_TO_NVARCHAR2(UTL_RAW.CAST_TO_RAW(TRANSLATE('IAMNVARCHAR2STRING'USINGNCHAR_CS)))FROMDUAL)
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i am nvarchar2 string
SQL>
问题解决。