Question

我在想是否有更高级的方法在mysql查询中使用ORDER BY。

我有查询从db获取产品，使用按价格排序。问题是如果折扣价值不为空，它会覆盖主要价格，而且应该以某种方式覆盖ORDER BY行。

IDEA：

DESC

product_price discount
900           0
800           0
1200          700 //dicount overrides price
600           0

查询有25行，但逻辑是这样的：

SELECT
product_price as price,
IFNULL(discount_amount,0) as discount

FROM not_relevant

WHERE not_relevant

ORDER BY product_price DESC

因此，当我根据价格将产品写入类别时，某些产品会有折扣，因此主要价格会被覆盖，仅按价格排序并不准确。

我尝试使用coalesce或两个ORDER BY。

有什么想法吗？谢谢你的帮助。

Answer 1

我认为这应该适合你：

SELECT
product_price,
IFNULL(discount_amount,0) as discount,
IFNULL(discount_amount,product_price) as price

FROM not_relevant

WHERE not_relevant

ORDER BY price DESC

它基本上就是你所要求的...如果discount不为空，则会使用它，否则它会使用product_price，并对结果进行排序。

Answer 2

如果折扣实际是折扣价而非折扣金额，则可以使用此

SELECT product_price as price,
IFNULL(discount_amount,0) as discount

FROM not_relevant
    ORDER BY 
CASE WHEN discount_amount IS NULL THEN price ELSE discount_amount END

Answer 3

SELECT product_price As price
     , Coalesce(discount_amount, 0) As discount
     , Coalesce(discount_amount, product_price) As order_by_this
FROM   not_relevant
WHERE  not_relevant
ORDER
    BY order_by_this

可替换地：

SELECT product_price As price
     , Coalesce(discount_amount, 0) As discount
FROM   not_relevant
WHERE  not_relevant
ORDER
    BY Coalesce(discount_amount, product_price)

mysql ORDER BY IF ELSE

3 个答案: