CODEWITHSUNDEEP
neo4jcypher
Mohelgamal
Mohelgamal

Reputation: 211

Can pattern be used with case in neo4j cypher

Is it possible to use patterns with a case statement in cypher ? specifically to return true or false if pattern exist. I am trying to model human relationships where friendship is not reciprocated.

So (user)-[:friend]->(user2) is a separate data point from (user2)-[:friend]->(user1)

Then I want to run a query that would show user1 who considers them their friends in return

something that would look like this (which doesn't work obviously)

MATCH (asker)-[:friend]->(target) RETURN CASE (target)-[:friend]->(asker)
WHEN present THEN true
ELSE THEN false As returnsFriendship

anyway to make that work ?

I know that a work around is to run a query looking for those who consider user1 friends and then loop through them outside cypher in my application but I was wondering if there is a pure cypher way to do this.

Upvotes: 0

Views: 230

Answers (1)

cybersam
cybersam

Reputation: 66967

The CASE clause is not the only way to get a boolean result, and is not necessary for your use case.

Patterns like (target)-[:teaches]->(asker) produce a (possibly empty) collection of paths, so this would work:

MATCH (asker), (target)
RETURN asker, target,
  SIZE((target)-[:teaches]->(asker)) > 0 AS returnsFriendship

But if only need to test for the existence of the pattern, using the EXISTS function would be better:

MATCH (asker), (target)
RETURN asker, target,
  EXISTS((target)-[:teaches]->(asker)) AS returnsFriendship

Upvotes: 2

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