cypher find which nodes have relation with a set of nodes

Question

From a previous query I retrieved a list of nodes, e.g. nodes 9,10,18,12,20 that indicate a car position. Note that the list can be dynamic, i may get more or less nodes

From the list of nodes i would like to know and retrieve which node is related to whom. (or who is friend of who) (node)-[:TO]-(node) From the given list

E.g. from the model, we can see that nodes 9 and 10 are (friends) related, 18 and 12 too and 20 has no friends from the list.

So at the end i would like to get this:

And in the Row result (in neo4j) should display

[9, 10], 
[18, 12], 
[20]

Each friend relation in a different row.

Any suggestions?

Thank you in advance

Answer 1

You can collect the nodes in your previous query and then UNWIND them and MATCH them onto themselves.

MATCH (n:Label)
// your filter here
WHERE ... 
WITH collect(DISTINCT n) AS my_nodes
// unwind twice to match nodes onto themselves
UNWIND my_nodes AS x
UNWIND my_nodes AS y
MATCH (x)-[:TO]->(y)
WHERE x <> y
RETURN x.value, y.value

But maybe you can also include this in you previous query somehow by including another relationship to the nodes? That depends how your previous query looks like.