"umeric or value error" in user function

Question

Hello everyone,
I wrote a very simple function which purpose is to format a Date (e.g. 31-12-2011) into this form: 2011-12
create or replace function inv_date (v_billing_month date)
return number is
begin
return to_char(v_billing_month,'yyyy-mm');
end inv_date;
The function is compiled without errors. But when I use the following skript I get an error:
select
inv_date(billing_month)
from bl_invdtl;
ORA-06502: PL/SQL: numeric or value error: character to number conversion error
To Problem seems to be, that the SQL-Statement expects a Date and not a character.
How can I avoid this error? Because the to_char() function generaly can do this.
Edited by: user10943421 on 01.02.2012 00:21

Answer 1

create or replace function inv_date (v_billing_month date)
return varchar2 is
begin
return to_char(v_billing_month,'yyyy-mm');
end inv_date;