You might be over thinking this... something like this might work out just fine. (I wouldn't necessarily do things this way, but rather keep a list of clauses and join them with " AND " to avoid keeping track of the "WHERE"s and "AND"s, but you get the point...)

    sql = 'SELECT * FROM products'
    args = []

    if title:
        sql += ' WHERE title LIKE %?%'
        args.append(title)

    if upc:
        if args:
            sql += ' AND'
        else:
            sql += ' WHERE'
        sql += ' upc LIKE %?%' 
        args.append(upc)

    if price_min:
        if args:
            sql += ' AND'
        else:
            sql += ' WHERE'
        sql += ' price >= ?'
        args.append(price_min)

    if price_max:
        if args:
            sql += ' AND'
        else:
            sql += ' WHERE'
        sql += ' price <= ?'
        args.append(price_max)

    if order_by_name:
        sql += ' ORDER BY name'
    elif order_by_price_low:
        sql += ' ORDER BY price'
    elif order_by_price_high:
        sql += ' ORDER BY price DESC'


    conn.query(sql, args)