在单个Cypher查询中返回两个聚合？

Question

我一直在努力与Cypher取得两个值的SUM并找出差异。我有这两个查询，它们查找一个节点的发送总数和接收的总数：

START addr = node(5)
MATCH addr <- [:owns] - owner - [to:transfers] -> receiver
RETURN SUM(to.value) AS Total_Sent

START addr = node(5)
MATCH addr <- [:owns] - owner <- [from:transfers] - sender
RETURN SUM(from.value) AS Total_Received

基本上，我的问题是-如何合并这两个单独的查询，以便可以区分Total_Sent和Total_Received？我已经尝试过多个起点，例如：

START sendAddr = node(5), receivedAddr = node(5)
MATCH sendAddr <- [:owns] - sendOwner - [to:transfers] -> receiver, receivedAddr <- [:owns] - receiveOwner <- [from:transfers] - sender
RETURN SUM(to.value) AS Total_Sent, SUM(from.value) AS Total_Received, SUM(to.value) - SUM(from.value) AS Balance

但是Total_Received为null！对我来说，这似乎是一个非常简单的用例-我到底在做什么错？

Answer 1

您不能像这样将两个查询粉碎在一起来合并两个查询。:)

为了解决这个问题，建议您使用WITH将查询分为两部分，如下所示：

START addr = node(5)
MATCH addr <- [:owns] - owner - [to:transfers] -> receiver
WITH addr, SUM(to.value) AS Total_Sent

MATCH addr <- [:owns] - owner <- [from:transfers] - sender
WITH SUM(from.value) AS Total_Received, Total_Sent

RETURN Total_Received, Total_Sent, Total_Received - Total_Sent as Total_Balance

HTH，

安德烈斯