I have not found the answer to this, so thought I’d go through the steps.
Assume we have a relational database with these tables:
USER (USER_ID, NAME, EMAIL)
LOT (LOT_ID, SLLER_ID, TYPE, DESCRIPTION, RESERVE_PRICE, START_DATE, END_DATE)
BID (BID_ID, LOT_ID, BIDDER_ID, BID_DATE, AMOUNT)
FEE (LOT_ID, AMOUNT)
What is the relational algebra that finds “the description and reserve price of any lot where all bids have been less than the reserve price”.
I have been struggling with this and came up with this:
But that will not work as will return any lot where a bid has been made for less than the reserve price.
I am sure this is a question of relational division but have not yet been able to get my mind round the right way to formulate it.