MySQL Sum positive and negative - 计算货币交易的确切总数

Question

我有一个充满事务的数据库表。交易包含来自返回人员的负数。我想把所有的金额字段加起来，同时从总数中减去返回的负值。我该怎么做并将其输出？ 目前我能做的最好的事情是:

  SELECT SUM(amount) 
  FROM outputaddition 
  GROUP by SIGN(amount);

但这只会将正数和负数放在同一列中。

Answer 1

SELECT personId,SUM(CASE WHEN amount<0 THEN amount ELSE 0 END) as NegativeTotal,
       SUM(CASE WHEN amount>=0 THEN amount ELSE 0 END) as PostiveTotal
FROM outputaddition
GROUP BY personID

如果你想要单列

SELECT personId,SUM(amount) as Total
FROM outputaddition
GROUP BY personID