Show all the books in database except the ones this specific user has read neo4j

Question

I have a simple database in Neo4j with information about users, their friends and the books they read. I need to write a query that shows all the books that were read by a specific user's friends (sort of a recommendation for the current user). Let's say I want to see the books that were read by the friends of user with name "Sophia". How can I do this in neo4j?

my database schema

Answer 1

You should be able to get those books by running the query below:

MATCH (sophia: User {name: "Sophia"})-[:FRIENDS_WITH]->(friends: User)-[:READ]->(book: Book)
RETURN book

If you want to only include books that haven't been read by Sophia, the query below should work:

MATCH (sophia: User {name: "Sophia"})-[:FRIENDS_WITH]->(friends: User)-[:READ]->(book: Book)
WHERE NOT EXISTS ((sophia)-[:READ]->(book))
RETURN book