Mysql SUM 的 SUM

Question

是否可以在一个选择查询中求和？

类似这样的事情:

SELECT id, SUM(current_price - bought_price)*amount AS profit FROM purchase WHERE purchase_id = 1 GROUP BY id 

我想要所有返回的利润的总和

Answer 1

这就是你要问的:

SELECT tmp.id, SUM(tmp.profit)
FROM (
  SELECT id, SUM(current_price - bought_price)*amount AS profit 
  FROM purchase 
  WHERE purchase_id = 1
  GROUP BY id 
) AS tmp

但是结果是一样的

SELECT SUM(current_price - bought_price)*amount AS profit 
FROM purchase 
WHERE purchase_id = 1