如果MySQL中的字段为null，则返回0

本文介绍了如果MySQL中的字段为null，则返回0的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！ 问题描述

在MySQL中，是否可以将总计"字段设置为零(如果它们为NULL)?

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

这就是我所拥有的:

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;

数据正常，除了NULL字段应为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)

从文档中:

如果expr1不为NULL，则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.