mysql - 一张表的SQL算术运算

Question

您好，我有交易表。 BigDecimal 金额和 bool 结果。如果结果为真，我就买了一些东西，如果结果为假，我就卖掉了一些东西。当我做这样的事情时，我想在单个查询中获取金额

SELECT (amount(when outcome is false) - amount(when outcome is true)) AS income 
FROM transaction WHERE (the condition I was unable to write);

有没有办法在单个查询中做到这一点？

Answer 1

我认为你只想要条件聚合:

SELECT SUM(CASE WHEN outcome THEN - amount ELSE amount END) as income 
FROM transaction;