CODEWITHSUNDEEP
neo4jcypher
Simon
Simon

Reputation: 537

neo4j cypher - Match node where another specific node of the same type doesn't exist

Background

I have a neo4j database set up with the following nodes;

(:game)-[:teamscore]-(:team)

The 'game' node would contain an id, a date and a name

The 'team' node link would contain an id, a teamname and an score.

Desired Outcome

I am looking to match nodes where teamname = "TeamA" but only where there isn't a linked node that exists with a different team for that 'game'.

(in plain English)

I want to return all nodes relating to a game where only 'TeamA' has scored (and not conceded).

What I have so far

MATCH(g:game)-[:teamscore]-(t:team)
WHERE g.team = "TeamA"
RETURN g, t

I thought about adding some kind of NOT (g)-[:teamscore]-(:team) to the WHERE clause but I'm not sure how I could do this in a way which doesn't eliminate the node which I do want to match.

Thanks in advance for any help on this!

Upvotes: 0

Views: 451

Answers (2)

Christophe Willemsen
Christophe Willemsen

Reputation: 20185

So, if the assumption is correct, there can be more than one (teamA)-[:teamscore]->(game) for the same game.

If yes, then you can make sure that all connections from game to a team node are to teamA.

Given the following graph :

CREATE (g:Game {id: 1})-[:teamscore]->(:Team {id: 1, name: "TeamA"})
CREATE (g)-[:teamscore]->(:Team {id:2, name: "TeamA"})
CREATE (g)-[:teamscore]->(:Team {id:3, name: "TeamA"})
CREATE (g2:Game {id: 2})-[:teamscore]->(:Team {name: "TeamA"})
CREATE (g2)-[:teamscore]->(:Team {name: "TeamB"})

You can use pattern comprehensions and the ALL predicate :

MATCH (n:Game)
WHERE ALL(x IN [(n)-[:teamscore]->(t) | t.name] WHERE x = "TeamA")
RETURN n

It will return Game with id 1

Upvotes: 0

Rajendra Kadam
Rajendra Kadam

Reputation: 4052

You can a match team by name and then make sure only one team is linked to that game by specifying the number of teamscore relationships to that game is 1.

MATCH(g:game)-[:teamscore]-(t:team) 
WHERE t.teamname = "TeamA" AND size((g)-[:teamscore]-(:team))=1 
RETURN g, t

Upvotes: 1

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