GraphAcademy

Intermediate Cypher Queries

Filtering Queries

Controlling Results Returned

Working with Cypher Data

Graph Traversal

Pipelining Queries

Reducing Memory

Using Parameters

OPTIONAL MATCH

Using OPTIONAL MATCH

Optionally returning rows

This query returns all the titles movies in the Film-Noir genre and the users who rated them.

cypher
MATCH (m:Movie)-[:IN_GENRE]->(g:Genre)
WHERE g.name = 'Film-Noir'
MATCH (m)<-[:RATED]-(u:User)
RETURN m.title, u.name

Currently it only returns movies that have also been rated.

Modify the query so that it returns all movies in the Film-Noir genre, regardless of whether they have been rated.

How many rows are returned?

  • ✓ 1152

Hint

You can make a MATCH clause optional by prefixing the OPTIONAL keyword.

Solution

The answer is 1152.

You can run the following query to see the result:

cypher
MATCH (m:Movie)-[:IN_GENRE]->(g:Genre)
WHERE g.name = 'Film-Noir'
OPTIONAL MATCH (m)<-[:RATED]-(u:User)
RETURN m.title, u.name

Summary

In this challenge, you modified a query and answered a question about what was retrieved which expanded the data returned to specify an OPTIONAL MATCH.

In the next module, you will learn about controlling results returned.