SELECT SUM(item1.price * sale_item1.qty) AS "July 10",
       SUM(DISTINCT(item2.price) * sale_item2.qty) AS "July 13"
FROM item item1 INNER JOIN sale_item sale_item1 ON ( item1.itemid = sale_item1.itemid)
                INNER JOIN sales sales1 ON
                ( sale_item1.saleid = sales1.saleid AND TO_CHAR(sales1.saledate, 'MM/DD') = '07/10'),
    item item2 INNER JOIN sale_item sale_item2 ON ( item2.itemid = sale_item2.itemid)
                INNER JOIN sales sales2 ON
                ( sale_item2.saleid = sales2.saleid AND TO_CHAR(sales2.saledate, 'MM/DD') = '07/13')