相关疑难解决方法(0)

在MySQL中,如果它们是NULL,有没有办法将"total"字段设置为零？

这是我有的:

SELECT uo.order_id, uo.order_total, uo.order_status,
            (SELECT SUM(uop.price * uop.qty) 
             FROM uc_order_products uop 
             WHERE uo.order_id = uop.order_id
            ) AS products_subtotal,
            (SELECT SUM(upr.amount) 
             FROM uc_payment_receipts upr 
             WHERE uo.order_id = upr.order_id
            ) AS payment_received,
            (SELECT SUM(uoli.amount) 
             FROM uc_order_line_items uoli 
             WHERE uo.order_id = uoli.order_id
            ) AS line_item_subtotal
            FROM uc_orders uo
            WHERE uo.order_status NOT IN ("future", "canceled")
            AND uo.uid = 4172;

数据很好,除了NULL字段应该是0.

如何在MySQL中为NULL返回0？