CODEWITHSUNDEEP
neo4jcypher
Oliver
Oliver

Reputation: 4173

Finding a parent node by its child nodes

What is the best way to find node A if I know the nodes C and B in Cypher?

  ┌────HAS_ITEM───┐                   
  │               ▼           
  │              .─.          
  │             ( C ) :ITEM   
 .─.             `─'          
( A )                         
 `─'                          
  │              .─.          
  └─HAS_ITEM───▶( B ) :ITEM   
                 `─'

My current query uses a MATCH ... WITH ... MATCH construction, but maybe there is way to express this in a better way?

Upvotes: 1

Views: 50

Answers (1)

Dave Bennett
Dave Bennett

Reputation: 11216

You can just create a single expression that finds A between both B and C 

CREATE INDEX ON :Item(name)


MATCH (b:Item {name: 'B'})<-[:HAS_ITEM]-(a)-[:HAS_ITEM]->(c:Item {name: 'C'})
RETURN a

If you had many items and you were looking for all of the items that shared that item you could do something like this.

// provide a list of values you want to match against
WITH ['B', 'C', 'D', 'E'] AS list

// find all of the matches
MATCH (a:Item)-[r:HAS_ITEM]->(b:Item)
WHERE b.name IN list

// collect the matched b nodes per a node
WITH list, a, collect(b) AS bs

// check to see if the matched number is the same as the input
WHERE size(bs) = size(list)
RETURN a

Upvotes: 3

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