How to match a node with over n relationships using neo4j's Cypher Query Language?-CodePudding

A node of a Round in a game is connected to Answer nodes.

(:Round)<-[:IN_ROUND]-(:Answer)

It is expected every Round to have 5 or fewer Answers related to it, I suspect there exists nodes in my database that have more than that, how can I query this information? Return all :Round nodes that have over 5 <-[:IN_ROUND]- relationships?

CodePudding user response：

You can use something like:

MATCH (n:Round)<-[:IN_ROUND]-(:Answer)
WHERE size((n)<-[:IN_ROUND]-(:Answer)) > 5
RETURN distinct(n)

You can see it works on this sample data:

MERGE (a:Round{key: 1})
MERGE (b:Round{key: 2})
MERGE (c:Answer{key: 3})
MERGE (d:Answer{key: 4})
MERGE (e:Answer{key: 5})
MERGE (f:Answer{key: 6})
MERGE (g:Answer{key: 7})
MERGE (h:Answer{key: 8})
MERGE (i:Answer{key: 9})

MERGE (c)-[:IN_ROUND{key:1}]-(a)
MERGE (d)-[:IN_ROUND{key:1}]-(a)
MERGE (e)-[:IN_ROUND{key:1}]-(a)
MERGE (f)-[:IN_ROUND{key:1}]-(a)
MERGE (g)-[:IN_ROUND{key:1}]-(a)
MERGE (h)-[:IN_ROUND{key:1}]-(a)
MERGE (i)-[:IN_ROUND{key:1}]-(b)
MERGE (c)-[:IN_ROUND{key:1}]-(b)
MERGE (e)-[:IN_ROUND{key:1}]-(b)
MERGE (f)-[:IN_ROUND{key:1}]-(b)
MERGE (g)-[:IN_ROUND{key:1}]-(b)

Returning:

╒═════════╕
│"n"      │
╞═════════╡
│{"key":1}│
└─────────┘

CodePudding user response：

You can use the WITH to count the number of connected nodes and then filter on this count.

If you wish to specify incoming connections to Round

MATCH (rnd:Round)<-[:IN_ROUND]-(a)
WITH rnd, count(a) as incomingNodes
WHERE incomingNodes>5
RETRUN rnd

If you want to count both incoming and outgoing connections:

MATCH (rnd:Round)-[:IN_ROUND]-(a)
WITH rnd, count(a) as connectedNodes
WHERE connectedNodes>5
RETRUN rnd