SQL and to_date problem

I want to query for all rows with a defined date:

select count(*)
from ia_artikel
where to_char( ausgabedatum, 'DD.MM.YY' ) = '28.09.99';

This works but the performance is poor. I think its because the conversation from date to char on each row. One other solution is to make a conversation on the static part:

select count(*)
from ia_artikel
where ausgabedatum = to_date('28.08.99','DD.MM.YY');

But this does not work! Why?

Bye,
Holger Received on Tue Sep 08 1998 - 11:49:49 CEST