SELECT *
FROM [Item]
WHERE Item.seller_id = ?

INNER JOIN Category
ON Item.category_id = Category.category_id

INNER JOIN Bid
ON Bid.item_id = Item.item_id
AND Bid.bid_id = 
    (
    SELECT MAX([bid_id]) 
    FROM Bid b2 
    WHERE [b2.item_id] = [Item.item_id]
    )