Stuff

SELECT *
FROM [Item]

INNER JOIN [Category]
ON [Item].[category_id] = [Category].[category_id]

INNER JOIN [Bid]
ON [Bid].[item_id] = [Item].[item_id]

WHERE [Item].[seller_id] = ?
AND [Bid].[bid_id] = 
    (
    SELECT MAX([bid_id]) 
    FROM [Bid] [b2]
    WHERE [b2].[item_id] = [Item].[item_id]
    )