如何在neo4j中找到没有传入关系的节点

Question

我有2个节点类型,可以说"学生"和"老师"类型

Student have {id, name}.
Teacher have {id, name}.

学生可以与班级节点建立可选关系,作为"教学".

(t:Teacher)-[r:TEACHES]->(c:Student).

[r:TEACHES] - Optional relationship. (present or may not present)

我想找到没有老师的"学生"节点.即没有任何传入关系"教学"

请帮忙.

Answer 1

我想你正在寻找这种模式.

MATCH (s:Student)
WHERE NOT (s)<-[:TEACHES]-(:Teacher)
RETURN s

Answer 2

这是一个简单的数据设置，以及解决问题所需的底部查询。本质上，您希望查询不存在关系的情况。这里的语法适用于 neo4j 2.0，因此旧版本的答案会略有不同。

neo4j-sh (?)$ create (t:Teacher {name:"Bob"})-[r:TEACHES]->(s:Student {name:"Mary"});
+-------------------+
| No data returned. |
+-------------------+
Nodes created: 2
Relationships created: 1
Properties set: 2
Labels added: 2
19 ms

neo4j-sh (?)$ create (t:Teacher {name:"Mark"});
+-------------------+
| No data returned. |
+-------------------+
Nodes created: 1
Properties set: 1
Labels added: 1
5 ms

neo4j-sh (?)$ MATCH (s:Student) WHERE NOT (s)<-[:TEACHES]-(:Teacher) RETURN s