Oracle 11g decode issue with null

Question

Hi,
we want to migrate from Oracle 10g to Oracle 11g and have an issue with decode.
The database has the following character set settings:
NLS_CHARACTERSET = AL32UTF8 in Oracle 11g and UTF8 in Oracle 10g
NLS_NCHAR_CHARACTERSET = AL16UTF16
If I try a select with decode which has null as first result argument I will get a wrong value.
select decode(id, null, null, name) from tab1;
("name" is a NVARCHAR2 field. Table tab1 has only one entry and "id" is not null.)
This select returns a value with characters which are splitted by 0 bytes.
In Oracle 10g the value without 0 bytes is delivered.
If I suround the decode with dump I get following results:
select dump(decode(id, null, null, name), 1016) from tab1;
Oracle 10g: Typ=1 Len=6 CharacterSet=AL32UTF8: 4d,61,72,74,69,6e
Oracle 11g: Typ=1 Len=12 CharacterSet=US7ASCII: 0,4d,0,61,0,72,0,74,0,69,0,6e
NLS_LANG has no effect on the character set of 'null' in Oracle 11g.
Non null literals work:
select dump(decode(id, null, 'T', name), 1016) from tab1;
Oracle 10g: Typ=1 Len=6 CharacterSet=UTF8: 4d,61,72,74,69,6e
Oracle 11g: Typ=1 Len=6 CharacterSet=AL32UTF8: 4d,61,72,74,69,6e
select dump(decode(id, null, N'T', name), 1016) from tab1;
Oracle 10g: Typ=1 Len=12 CharacterSet=AL16UTF16: 0,4d,0,61,0,72,0,74,0,69,0,6e
Oracle 11g: Typ=1 Len=12 CharacterSet=AL16UTF16: 0,4d,0,61,0,72,0,74,0,69,0,6e
Here the scripts for creating the table and the entry:
create table tab1 (
id NUMBER(3),
name NVARCHAR2(10)
insert into tab1 (id, name) values (1, N'Martin');
commit;
Is it possible to change the character set?
Could you please help me?
Regards
Martin

Answer 1

This doesn't have the problem.looks this doesn't solve the problem (of returning a value with characters which are splitted by 0 bytes):
SQL> select * from v$version where rownum = 1
BANNER                                                                         
Oracle Database 11g Enterprise Edition Release 11.2.0.1.0 - Production         
1 row selected.
SQL> select dump(decode(id, null, null, name), 1016) from tab1
union all
select dump(case id when null then null else name end, 1016) cs from tab1
DUMP(DECODE(ID,NULL,NULL,NAME),1016)                                           
Typ=1 Len=12 CharacterSet=US7ASCII: 0,4d,0,61,0,72,0,74,0,69,0,6e              
Typ=1 Len=12 CharacterSet=AL16UTF16: 0,4d,0,61,0,72,0,74,0,69,0,6e             
2 rows selected.You need to explicitly convert the third parameter to char:
SQL> select dump(decode(id, null, to_char(null), name), 1016) from tab1
DUMP(DECODE(ID,NULL,TO_CHAR(NULL),NAME),1016)                                  
Typ=1 Len=6 CharacterSet=WE8MSWIN1252: 4d,61,72,74,69,6e                       
1 row selected.