€ Euro sign/symbol not showing up on Oracle 10gr2 and aix 6.1
Your database character set is WE8ISO8859P1, it doesn't have the € sign. Either use NVARCHAR2 or change your database character set (export, reinstall with a character set that supports the euro sign like WE8ISO8859P15 or AL32UTF8, and import).

Here's an example of NVARCHAR2:

SQL&gt; SELECT * FROM nls_database_parameters WHERE parameter LIKE '%SET';

PARAMETER                      VALUE
------------------------------ ----------------------------------------
NLS_NCHAR_CHARACTERSET         AL16UTF16
NLS_CHARACTERSET               WE8ISO8859P1


As you can see I am in the same situation as you.

SQL&gt; CREATE TABLE prueba (id NUMBER, euro NVARCHAR2(20));

Table created.

SQL&gt; INSERT INTO prueba VALUES (1, N'€');

1 row created.

SQL&gt; INSERT INTO prueba VALUES (2, UNISTR('\20AC'));

1 row created.    

SQL&gt; INSERT INTO prueba VALUES (3, NCHR(8364));

1 row created.

SQL&gt; INSERT INTO prueba VALUES (4, CHR(8364 USING NCHAR_CS));

1 row created.

SQL&gt; INSERT INTO prueba VALUES (5, '€');

1 row created.

SQL&gt; SELECT id, euro, ascii(euro) FROM prueba;

        ID EURO                 ASCII(EURO)
---------- -------------------- -----------
         1 €                           8364
         2 €                           8364
         3 €                           8364
         4 €                           8364
         5 ¿                            191