CODEWITHSUNDEEP
neo4jcypher
Patrick Kowalski
Patrick Kowalski

Reputation: 23

Neo4j getting child nodes of multiple parents

I've just recently started using neo4j and I've run into an issue. There doesn't seem to be an answer to this on here but I might also be wording it incorrectly. I'm building a small site that categorizes music. There are multiple song nodes with BELONGS_TO relationships to genre nodes. How can I get every song that belongs to a set of user specified genres.

For example. Song1, Song2, Song3 all belong to both Pop and Electronic. Song4 just belongs to Pop. How can I query to get every song belonging to both Pop and Electronic? In this case Song1, Song2, an Song3.

I've been struggling with this for a while. This is what I have so far but it doesn't return anything. If I replace AND with OR I get all the songs that belong to one of those genres.

MATCH (n:Song)-[r:BELONGS_TO]->(Genre)
WHERE (n)-[r]->(Genre{name:"Pop"}) AND (n)-[r]->(Genre{name:"Electronic"})
RETURN n

Thank you.

Upvotes: 2

Views: 1167

Answers (1)

FrobberOfBits
FrobberOfBits

Reputation: 18022

What you're trying to do in the WHERE clause you should actually do in the MATCH clause. Here you go:

MATCH (g1:Genre {name: "Pop"})<-[:BELONGS_TO]-(popElectronicSongs:Song)-[:BELONGS_TO]->(g2:Genre {name: "Electronic"});
RETURN popElectronicSongs;

You can actually do quite a lot with just the MATCH clause as you can see here. The WHERE bit usually gets used for filtering based on various predicates. For example you might say WHERE popElectronicSongs.title =~ /S.*/ to filter for only songs whose name starts with S.

Upvotes: 2

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