How to formate date in where clause?

I tried to run a query:

select a,b c
from d_table
where drop_date = sysdate - 1;

However, I coundn't get value return even I know there are rows matched to the query. I understand there must some way to format date. Can anyone help?

Thansk.
Maggie Received on Thu Jun 08 2000 - 00:00:00 CDT