On the Webi side, if then else replaces case expressions and CurrentDate() replaces sysdate:
=Count([Product No]) Where ([Sales Date]<CurrentDate())
If you're creating a Universe level object, use:
COUNT(CASE WHEN SALES.SALES_DATE < SYSDATE THEN SALES.PRODUCT_NO END)
If you have ELSE 0 at the end, you'd count the 0 and end up with a wrong answer.
Regards,
Mark