Cannot delete node<id>, because it still has relationships. To delete this node, you must first delete its relationships

Neo4j Graph Platform Cypher
1

I am creating relations between nodes n and l.
Sometimes duplicate relations occur.
image

If a relation of this type already exists, it should merge.
So to be clear: only the relation should merge - not the nodes.
Unfortunately I have not found something like apoc.refactor.mergeRels, som i am using mergeNodes.

image
image1317×866 51.1 KB

I get this exception, that i need to delete the relationships first. But how do I integrate a deletion of relationships into this query?

Here are the query that gives the exception (same as above from picture)

MATCH(n) WHERE ID(n) = {fromNodeId}
MATCH(l) WHERE ID(l) = {toNodeId} 
CREATE (n)-[r:{relationType}]->(l)
WITH n,l
MATCH (n)-[r:{relationType}]->(l) 
WITH n ORDER BY n.creationTime DESC
WITH collect(n) AS origin 
CALL apoc.refactor.mergeNodes(origin, { properties: 'discard',  mergeRels:true}) 
YIELD node 
RETURN node

Thank you!

2

You can use the command

MATCH (n:yourNode)..
DETACH DELETE n

Andy

1 Like
3

EDIT:

I have found apoc.merge.relationship
The problem of duplicate relations continues

WITH n,l
CALL apoc.merge.relationship
(
  n,'{relationType}',{},{},l,{}
) 
YIELD rel
RETURN rel

Now even more so, as relation between nodes that are neither (n) nor (l) will be created and duplicated

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image681×749 42.2 KB

4

I'm getting this same error message while trying to use:

CALL apoc.refactor.mergeNodes([n, n2])

to merge duplicate nodes. Did you find a solution?

5 
Try this:

MATCH (a:Name)-[r]->(b:Name)
WITH a, collect(r) as rels, b
WHERE size(rels) > 1
UNWIND tail(rels) as rel
DELETE rel
return a, b
6

That's a good method