CODEWITHSUNDEEP
neo4jcypher
user18837670
user18837670

Reputation:

How to set a count(variable) as a property of a node

I'm currently trying to get the count of all movies that each actor has acted in (neo4j example movie database), and then set that as a num_movies_acted attribute for the person node.

So far, I'm able to get a list of all the actors and their respective movie count (including if it's 0 because of the OPTIONAL MATCH)

This is what I have:

MATCH (p:Person)
OPTIONAL MATCH (p)-[:ACTED_IN]->(m:Movie)
RETURN p.name as name, count(m) as num_movies_acted

How would I then set that into the Person Node? I know I should use something like:

SET p.num_movies_acted = count(m), but that fails to work.

Invalid use of aggregating function count(...) in this context (line 3, column 26 (offset: 84))
"SET p.num_movies_acted = count(m)"

EDIT: Would this work?

MATCH (p:Person)
OPTIONAL MATCH (p)-[:ACTED_IN]->(m:Movie)
WITH p, count(m) as num_movies_acted
SET p.num_movies_acted = num_movies_acted
RETURN p

since I am "storing" the count(m) into a variable first

Upvotes: 0

Views: 854

Answers (2)

Nao Ito
Nao Ito

Reputation: 79

This is a note for someone expecting a tree with an aggregation property.

I need a tree( Person-[ACTED_IN]->Movie ) with p.num_movies_acted, so finally I got a cypher:

MATCH (p:Person)-[r:ACTED_IN]->(m:Movie)
  WHERE m.released > 2000
  WITH p, count(r) as num_movies_acted
MATCH (p:Person)-[r:ACTED_IN]->(m:Movie)
  WHERE m.released > 2000
SET p.num_movies_acted = num_movies_acted
RETURN p,r,m

I got the same error of aggregation, so tried to somehow avoid it.
I'm not confident in it. So, kindly tell me more efficient one.

Upvotes: 0

micro5
micro5

Reputation: 415

MATCH (p:Person) OPTIONAL MATCH (p)-[:ACTED_IN]->(m:Movie) RETURN p.name as name, count(m) as num_movies_acted

This query returns a list as num_movies_acted, which fails to work when you try to set it as an property of an individual node.

EDIT: Would this work?

MATCH (p:Person) OPTIONAL MATCH (p)-[:ACTED_IN]->(m:Movie) WITH p, count(m) as num_movies_acted SET p.num_movies_acted = num_movies_acted RETURN p

Yes this would work fine as you are counting the Movie node for each of the Person node and setting the property.

You can also try:

MATCH (p:Person)
OPTIONAL MATCH (p)-[r:ACTED_IN]->(m:Movie)
WITH p, count(r) as num_movies_acted
SET p.num_movies_acted = num_movies_acted
RETURN p

Upvotes: 1

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