Question

我正在开发一个带有MySQL数据库的PHP应用程序，该数据库存储了公司所做的交易清单。

这些销售和购买都保存在同一个表格中，标识符列中包含p或s。

我希望通过将salesOrPurchase ='s'的所有交易全部加起来计算利润，然后对salesOrPurchase ='p'进行相同的操作，然后从我们的销售中扣除我们的购买以计算出利润。

有些事情：

SELECT
SUM(amount) WHERE salesOrPurchase = 's' as SalesTotal,
SUM(amount) WHERE salesOrPurchase = 'p' as PurchasesTotal,
(SalesTotal - PurchasesTotal) as Profit
FROM transactions

Answer 1

子查询怎么样？

SELECT SalesTotal, PurchasesTotal, (SalesTotal-PurchasesTotal) as Profit
FROM (SELECT (SELECT SUM(amount) FROM transactions WHERE salesOrPurchase = 's') as SalesTotal,
             (SELECT SUM(amount) FROM transactions WHERE salesOrPurchase = 'p') as PurchasesTotal
     ) t

Answer 2

您不能在定义它们的同一select中使用别名。相反，对所有三个使用条件聚合：

SELECT SUM(case when salesOrPurchase = 's' then amount end) as SalesTotal,
       SUM(case when salesOrPurchase = 'p' then amount end) as PurchasesTotal,
       SUM(case when salesOrPurchase = 's' then amount
                when salesOrPurchase = 'p' then - amount
           end)  as Profit
FROM transactions;

PHP / MySQL - 通过添加销售和购买然后减去来计算利润

2 个答案: