尝试了解MATCH和WHERE中的标识符和集合 [英] Trying to understand identifiers and collections in MATCH and WHERE

问题描述

我试图了解某些标识符或表达式对应于哪种密码数据结构"，具体取决于如何使用它们以及在何处使用它们. 下面，我列出了我遇到的示例.请告诉我我是否正确(在评论中)或我缺少什么.

I am trying to understand to what kind of cypher "data structure" certain identifiers or expressions correspond to, depending on how and where they are used. Below I list examples I encountered. Please tell me if I got it right (in the comments) or if I am missing something.

MATCH (a:MYTYPE { label:'l_a' })
// a corresponds to a collection of nodes

MATCH (b:MYTYPE { label:'l_b' })
// so does b

MATCH p=(a)-[sp1:CF*]->(b)-[sp12:CF]->(c)
// p corresponds to a collection of paths
// a and b correspond to a collection of nodes 
// (or does the previous MATCH of a and b change something?)
// sp1 corresponds to a collection of collections of relationships
// sp12 corresponds to a collection of relationships
// c corresponds to a collection of nodes

WHERE ( p = ... )
// Here, the p corresponds to a path, i.e. there must be a path or (I don't know) on the right side of the =
WHERE ( a = ... )
// a corresponds to a node, i.e. there must be a node on the right side of the =
WHERE ( sp1 = ... )
// sp1 corresponds to a collection of nodes, i.e. there must be a collection of relationships on the right side

//BONUS:
WHERE ( (e)-[sp2:CF*]->(f) ) = ...
// there must be a collection of collections of paths on the right side of the =

推荐答案

我认为回答所有这些问题的最简单方法是将标识符传递给函数，该函数会引发错误，告诉您期望值和实际接收值.我认为您还应该谨慎使用单词集合，因为它是不正确的.

I think the easiest way to answer all these questions is by passing identifiers to functions that will throw an error telling you what it expected and what it actually received. I think you should also be careful about how you use the word collection, as it is not correct.

MATCH (n) RETURN n;

n是Node.

MATCH ()-[r]-() RETURN r;

r是Relationship.

MATCH p = ()-[]-()

p是Path.

MATCH (n) WITH COLLECT(n) AS c RETURN c;

c是Collection<Node>.

MATCH ()-[r]-() WITH COLLECT(r) AS c RETURN c;

c是Collection<Relationship>.

MATCH p = ()-[]-() WITH COLLECT(p) AS c RETURN c;

c是Collection<Path>.

MATCH p = ()-[r*..2]-() RETURN p, r;

p是Path.

r是Collection<Relationship>.

并参考您的特定示例:

MATCH p = (a)-[sp1:CF*]->(b)-[sp12:CF]->(c)

p是Path.

a是Node.

sp1是Collection<Relationship>.

b是Node.

sp12是Relationship.

c是Node.

我不确定您对WHERE子句的要求是什么.也许您可以通过编辑问题来澄清问题.

And I'm not sure what you're asking about the WHERE clauses. Perhaps you can clarify with an edit to your question.

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