Neo4j Cypher query - collect elements from 2 different variables to single list

Question

I have a following part of Cypher query:

MATCH (ch:Characteristic) WHERE id(ch) = {characteristicId} WITH ch OPTIONAL MATCH (ch)<-[:SET_ON]-(v:Value)...

first of all I'm looking for (ch:Characteristic) by characteristicId and then applying required logic for this variable at the rest of my query.

my Characteristic can also have(or not) a child Characteristic nodes, like:

(ch:Characteristic)-[:CONTAINS]->(childCh)

Please help to extend my query in order to collect ch and childCh into a list of Characteristic thus I'll be able at the rest of my query to apply required logic to all Characteristic at this list.

UPDATED - possible solution #2

This is my current working query:

MATCH (chparent:Characteristic) 
WHERE id(chparent) = {characteristicId} 
OPTIONAL MATCH (chparent)-[:CONTAINS*]->(chchild:Characteristic) 
WITH chparent, collect(distinct(chchild)) as childs 
WITH childs + chparent as nodes 
UNWIND nodes as ch 
OPTIONAL MATCH (ch)<-[:SET_ON]-(v:Value)-[:SET_FOR]->(Decision) 
OPTIONAL MATCH (v)-[:CONTAINS]->(vE) OPTIONAL MATCH (vE)-[:CONTAINS]->(vEE) 
OPTIONAL MATCH (ch)-[:CONTAINS]->(cho:CharacteristicOption) 
OPTIONAL MATCH (cho)-[:CONTAINS]->(choE) OPTIONAL MATCH (ch)-[:CONTAINS]->(chE) 
DETACH DELETE choE, cho, ch, vEE, vE, v, chE

This is an attempt to simplify the query above:

MATCH (ch:Characteristic) 
WHERE (:Characteristic {id: {characteristicId}})-[:CONTAINS*]->(ch) 
OPTIONAL MATCH (ch)<-[:SET_ON]-(v:Value)-[:SET_FOR]->(Decision) 
OPTIONAL MATCH (v)-[:CONTAINS]->(vE) 
OPTIONAL MATCH (vE)-[:CONTAINS]->(vEE) 
OPTIONAL MATCH (ch)-[:CONTAINS]->(cho:CharacteristicOption) 
OPTIONAL MATCH (cho)-[:CONTAINS]->(choE) 
OPTIONAL MATCH (ch)-[:CONTAINS]->(chE) 
DETACH DELETE choE, cho, ch, vEE, vE, v, chE

but this query doesn't delete required Characteristic nodes and my tests fail. What am I doing wrong at the last query ?

Answer 1

You can try something like this with apoc:

MATCH (chparent:Characteristic {characteristicId: <someid>})
OPTIONAL MATCH (chparent)-[:CONTAINS]->(chchild:Characteristic)
WITH apoc.coll.union(chparent,chchild) as distinctList
...

With pure cypher you can try something like this:

MATCH (chparent:Characteristic {characteristicId: <someid>})
OPTIONAL MATCH (chparent)-[:CONTAINS]->(chchild:Characteristic)
WITH chparent,collect(distinct(chchild)) as childs
WITH chparent + childs as list
....

Not really sure if you need distinct in collect, but I added just so you know you can do this to filter out duplicates.

Answer 2

You can actually do this easily by using a variable-length relationship match of 0..1, as it will let you match on your root :Characteristic node and any of its children.

MATCH (chparent:Characteristic)-[:CONTAINS*0..1]->(ch:Characteristic)
WHERE id(chparent) = {characteristicId} 
// ch contains both the parent and children, no need for a list
...

Answer 3

A more simplified query.

MATCH (c:Characteristics) WHERE (:Characteristics {id: 123})-[:CONTAINS*0..1]->(c) return c;

Matches all Characteristics including the root node that (optionally) have incoming relationships of type CONTAINS from the node specified with id 123.

Answer 4

I assume all the children of Characteristic will also have the label Characteristic. Another assumption I made is, you need characteristicId which is defined by you, not the internal id defined by neo4J. id(ch) fetching the internal id instead of user defined ID. You might want to pass the characteristicId variable like I gave here.

MATCH (chparent:Characteristic {characteristicId: <someid>})
WITH chparent
OPTIONAL MATCH (chparent)-[:CONTAINS]->(chchild:Characteristic)
WITH chchild
<your operation>