图数据库中的关系如图：

我想查询CarC涉及的交通事故中有多少次属于单方事故（即只有一辆车与某事故相关联），以上图为例，CarC的单方事故次数应为6（C1-C6）。

我的想法是：

1. 先算出CarC涉及的总事故次数total：

match (c1:Car)-[:INVOLVE]-(a1:Accident)
where c1.name = "CarC"
with count(distinct a1) as total
return total

得到 total = 7

1. 然后算双方事故次数bin：

match(c1:Car)-[:INVOLVE]-(a2:Accident)-[:INVOLVE]-(c2:Car)
where c1.name = "CarC"
with count(distinct a2) as bin
return bin

得到 bin = 1

因此我想使用下面语句将前面两个查询合并：

match (c1:Car)-[:INVOLVE]-(a1:Accident), (c1)-[:INVOLVE]-(a2:Accident)-[:INVOLVE]-(c2:Car)
where c1.name = "CarC"
with count(distinct a1) as total, count(distinct a2) as bin
return total,bin

这样得到的结果却是：toatal = 6， bin = 1

请问为什么会不一样？