Neo4j，后续 MATCH 路径查询

Question

我试图编写一个包含多个匹配项的 Cypher 查询以获取多个路径

查询

MATCH (a:A) --> (b:B) where b.uid="asdfas"
MATCH path = (a) -> (leaf) with collect(path) as paths
MATCH another_path = (b) -> (leaf) with collect(another_path) as paths_2

RETURN paths, paths_2

结果

Neo.ClientError.Statement.SyntaxError: Variable `paths` not defined 
"RETURN paths, paths_2"

return 子句忘记了path

与上面不同，如果 MATCH 只产生节点而不是路径列表

MATCH (a:A) --> (b:B) where b.uid="asdfas"
MATCH path = (a) -> (leaf) with collect(path) as paths
MATCH (b) --> (c:C) 

RETURN paths, c

上述查询完美执行。

Answer 1

WITH 子句导致所有现有变量变为未绑定除了WITH 子句继续传递的变量。

第一个WITH必须通过b，这样后面的MATCH才能使用。而第二个WITH 必须通过paths 才能返回：

MATCH (a:A)-->(b:B) WHERE b.uid="asdfas"
MATCH path = (a)->()
WITH b, COLLECT(path) AS paths
MATCH another_path = (b)->()
WITH paths, COLLECT(another_path) AS paths_2
RETURN paths, paths_2

更好的是，实际上不需要您的第二个WITH：

MATCH (a:A)-->(b:B) WHERE b.uid="asdfas"
MATCH path = (a)->()
WITH b, COLLECT(path) AS paths
MATCH another_path = (b)->()
RETURN paths, COLLECT(another_path) AS paths_2

Answer 2

在您的第一个查询中，您需要将paths 添加到您的最终with 语句中，以便它可用于RETURN 语句。

MATCH another_path = (b) -> (leaf) with collect(another_path) as paths_2, paths

就个人而言，我喜欢将WITH（和WHERE）语句放在不同的行中，以使这些事情可能更清楚地了解正在传递的内容

MATCH (a:A) --> (b:B) 
WHERE b.uid="asdfas"

MATCH path = (a) -> (leaf) 
WITH collect(path) as paths

MATCH another_path = (b) -> (leaf) 
WITH collect(another_path) as paths_2, paths

RETURN paths, paths_2