The parameter of SQL function 'unistr'

Question

Hi guys,
Today I tried with SQL function 'unistr', found it strange in the parameter...
My environment:
Oracle Database 11g Enterprise Edition Release 11.2.0.2.0 - 64bit Production
PL/SQL Release 11.2.0.2.0 - Production
CORE    11.2.0.2.0    Production
TNS for Linux: Version 11.2.0.2.0 - Production
NLSRTL Version 11.2.0.2.0 - Production
and
Oracle Database 11g Enterprise Edition Release 11.2.0.3.0 - 64bit Production
PL/SQL Release 11.2.0.3.0 - Production
"CORE    11.2.0.3.0    Production"
TNS for Solaris: Version 11.2.0.3.0 - Production
NLSRTL Version 11.2.0.3.0 - Production
client is PL/SQL Developer 7.1.4.1390
As documented, I tried with a Unicode encoding value, but got blank (not a NULL):
SELECT unistr('\00f6') FROM dual;
but when I tried a value with some character appended, it worked:
SELECT unistr('\00f6 ') FROM dual;
ö
SELECT unistr('\00f6a') FROM dual;
ö
SELECT unistr('\00f6*') FROM dual;
ö
Is it caused by the client, anyone helps?

Answer 1

When I tried sqlplus, I got the same result as you, I believe it's from the client.
My character set is OK I think, it's from sqlplus:
SQL> SELECT * FROM v$version;
BANNER
Oracle Database 11g Enterprise Edition Release 11.2.0.3.0 - 64bit Production
PL/SQL Release 11.2.0.3.0 - Production
CORE    11.2.0.3.0      Production
TNS for Solaris: Version 11.2.0.3.0 - Production
NLSRTL Version 11.2.0.3.0 - Production
SQL> SELECT *
  2    FROM v$nls_parameters
  3   WHERE parameter IN ('NLS_CHARACTERSET', 'NLS_NCHAR_CHARACTERSET');
PARAMETER
VALUE
NLS_CHARACTERSET
AL32UTF8
NLS_NCHAR_CHARACTERSET
AL16UTF16
SQL> SELECT unistr('\00f6') FROM dual;
U
÷
SQL> SELECT unistr('\00f6*') FROM dual;
UN
÷*
But in PL/SQL Developer, the tricky things happen:
Connected to Oracle Database 11g Enterprise Edition Release 11.2.0.3.0
Connected as xxx
SQL> SELECT unistr('\00f6') FROM dual;
UNISTR('\00F6')
SQL> SELECT unistr('\00f6*') FROM dual;
UNISTR('\00F6*')
ö
SQL> SELECT unistr('\00f6') FROM dual UNION ALL SELECT unistr('\00f6*') FROM dual;
UNISTR('\00F6')
ö
ö
SQL>
And I tried with dbms_output.put_line to output the character, it's correct.