如果字段在 MySQL 中为 null，则返回 0

Return 0 if field is null in MySQL(如果字段在 MySQL 中为 null，则返回 0)

问题描述

在 MySQL 中，如果总计"字段为 NULL，是否可以将它们设置为零?

In MySQL, is there a way to set the "total" fields to zero if they are NULL?

这是我所拥有的:

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.

The data comes out fine, except the NULL fields should be 0.

如何在 MySQL 中为 NULL 返回 0?

How can I return 0 for NULL in MySQL?

推荐答案

使用 IFNULL:

IFNULL(expr1, 0)

来自文档:

如果 expr1 不为 NULL，IFNULL() 返回 expr1；否则返回 expr2.IFNULL() 返回数字或字符串值，具体取决于使用它的上下文.

If expr1 is not NULL, IFNULL() returns expr1; otherwise it returns expr2. IFNULL() returns a numeric or string value, depending on the context in which it is used.

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