I haven't tested, but this should work.

CREATE FUNCTION dbo.fn_ck_newBidIsHigher(@auction int, @bid numeric(8,2))
RETURNS bit
BEGIN
  RETURN (SELECT CAST(CASE WHEN EXISTS( SELECT 1 FROM Bid WHERE...

It's great that you found a solution and posted it on here. Thank you very much for doing it.

I can post a solution for this but it would work on SQL Server. You're working with Oracle, so you should check on an Oracle forum or http://stackoverflow.com/

I've always find simpler to use cross-tabs instead of the pivot operator. It's more flexible and it can become simpler and faster.

SELECT BookType,
   SUM( CASE...

One more vote for this.