Question

我在下面有一个查询，而且sales_creditmemo表中的所有值都不存在于sales_order_item表中，所以很多“Totaal_inclusief BTW en excl credit”都是NULL。如何将c.base_grand_total设为0而不是NULL，因此总数为b.base_grand_total而不是NULL

SELECT a.order_id AS "Ordernummer", a.created_at AS "Orderdatum", 
b.base_grand_total AS "Inclusief BTW", b.base_tax_amount AS "Berekende BTW", 
c.base_grand_total AS  "Credit-terugbetaald",
(b.base_grand_total - c.base_grand_total) AS "Totaal_inclusief BTW en excl 
credit" FROM `sales_order_item` a 
INNER JOIN sales_invoice b ON a.order_id = b.order_id
LEFT JOIN sales_creditmemo c ON a.order_id = c.order_id
WHERE a.created_at > '2017-01-01'
GROUP BY a.order_id

Answer 1

使用coalesce功能：

SELECT  a.order_id AS "Ordernummer", 
        a.created_at AS "Orderdatum", 
        b.base_grand_total AS "Inclusief BTW", 
        b.base_tax_amount AS "Berekende BTW", 
        c.base_grand_total AS  "Credit-terugbetaald",
        (b.base_grand_total - coalesce(c.base_grand_total, 0)) AS "Totaal_inclusief BTW en excl 
credit" 
FROM `sales_order_item` a 
INNER JOIN sales_invoice b ON a.order_id = b.order_id
LEFT JOIN sales_creditmemo c ON a.order_id = c.order_id
WHERE a.created_at > '2017-01-01'
GROUP BY a.order_id

当空切换为0时，mysql左连接NULL

1 个答案: