Ecto：添加查询结果
我是凤凰城的新手，我有一张积分表。我试图从一种积分中扣除另一种积分。
q1 = from p in Point, where: (p.i_id == ^user), select: sum(p.points)
claims = Repo.all(q1)
q2 = from c in Point, where: (c.r_id == ^user), select: sum(c.points)
points = Repo.all(q2)
balance = points - claims
但我得到了
bad arithmetic expression
如何添加或减去查询结果？
I'm new to Phoenix and I have a points table. I'm trying to deduct one kind of points from another kind of points.
q1 = from p in Point, where: (p.i_id == ^user), select: sum(p.points)
claims = Repo.all(q1)
q2 = from c in Point, where: (c.r_id == ^user), select: sum(c.points)
points = Repo.all(q2)
balance = points - claims
But I get
bad arithmetic expression
How do I add or subtract query results?
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Repo.all将始终返回一个列表，如下所示：[1]。请改用
Repo.one，它将返回单个值，例如1。Repo.allwill always return a list, like this:[1].Use
Repo.oneinstead, which will return a single value, e.g.1.