Training Week: Introduction to Neo4j

Neo4j, Inc. All rights reserved 2021
Introduction to Neo4j -
a hands-on crash course
Lju Lazarevic
Developer Relations
@ElLazal
dev.neo4j.com/forum
dev.neo4j.com/chat

In this session
We will cover:
• What is a graph and why they are amazing
• Spotting good graph scenarios
• Property graph database anatomy and introduction to Cypher
• Hands-on: the movie graph on Neo4j Aura Free
◦ dev.neo4j.com/aura-login
• Continuing your graph journey
Useful reference: https://dev.neo4j.com/rdbms-gdb

What is a graph?

A graph is...
...a set of discrete objects, each of which has some set of relationships with the
other objects
Seven Bridges of Konigsberg problem. Leonhard Euler, 1735

Anything can be a graph
the Internet a water molecule
H
O
H

Why are graphs amazing?

Follow the flow - buying trainers

Panama papers:
simple model, powerful outcome

10
The Panama papers data
model...

Roses are red,
facebook is blue,
No mutual friends,
So who are you?

Friends of friends
...or co-actors of co-actors

What are good graph scenarios?

Scenario 1: Does our problem involve understanding relationships between
entities?
Identifying good graph scenarios
● Recommendations
● Fraud detection
● Finding duplicates
● Data lineage

Scenario 2: Does the problem involve a lot of self-referencing to the same type
of entity?
● Organisational
hierarchies
● Access management
● Social influencers
● Friends of friends

Scenario 3: Does the problem explore relationships of varying or unknown
depth?
● Supply chain
visibility
● Bill of Materials
● Network
management

Scenario 4: Does our problem involve discovering lots of different routes or
paths?
● Logistics and routing
● Infrastructure
management
● Dependency tracing

So what does a (property) graph
look like?

Node (Vertex)
● The main data element from which graphs are constructed
19
Graph components
Jane car

20
Graph components
Node (Vertex)
● The main data element from which graphs are constructed
Relationship (Edge)
● A link between two nodes. Has:
○ Direction
○ Type
● A node without relationships is permitted. A relationship without nodes is not
Jane car
OWNS

21
Property graph database
Node (Vertex)
Relationship (Edge)
OWNS

22
Node (Vertex)
Relationship (Edge)
:Person :Car
OWNS
Label
● Define node category (optional)

23
Node (Vertex)
Relationship (Edge)
:Person :Car
OWNS
Label
● Can have more than one
:Asset

24
Node (Vertex)
Relationship (Edge)
:Person :Car
OWNS
Label
● Can have more than one
Properties
● Enrich a node or relationship
● No need for nulls!
name: Jane make: Volvo
model: V60
since: 2018
:Asset

How do I query the graph?

Neo4j, Inc. All rights reserved 2021 26

Cypher
A pattern-matching query language made for graphs


Cypher
A pattern matching query language made for graphs
• Declarative
• Expressive
• Pattern-Matching


Cypher
A pattern matching query language made for graphs
• Declarative
• Expressive
• Pattern Matching
With ASCII ART ¯_(ツ)_/¯

Nodes and relationships at a glance
Description Node Relationship
Generic () -- --> -[]-
With a reference (n) -[r]-
With a node label or rel
type
(:Person) -[:ACTED_IN]-
With a label/type and an
inline property
(:Person {name: ‘Bob’}) -[:ACTED_IN {role: ‘Dave’}]-
With a reference,
label/type and an inline
property
(p:Person {name: ‘Bob’})
-[r:ACTED_IN {role:
‘Rob’}]-

Use MATCH to retrieve nodes
//Match all nodes
MATCH (n)
RETURN n;

//Match all nodes
MATCH (n)
RETURN n;
//Match all nodes with a Person label
MATCH (n:Person)
RETURN n;

//Match all nodes
MATCH (n)
RETURN n;
//Match all nodes with a Person label
MATCH (n:Person)
RETURN n;
//Match all nodes with a Person label and property name is "Tom Hanks"
MATCH (n:Person {name: "Tom Hanks"})
RETURN n;

//Return nodes with label Person and name property is "Tom Hanks" -
Inline
MATCH (p:Person {name: "Tom Hanks"}) //Only works with exact matches
RETURN p;
Use MATCH and properties to retrieve nodes

Inline
RETURN p;
//Return nodes with label Person and name property equals "Tom Hanks"
MATCH (p:Person)
WHERE p.name = "Tom Hanks"
RETURN p;

Inline
RETURN p;
//Return nodes with label Person and name property equals "Tom Hanks"
MATCH (p:Person)
WHERE p.name = "Tom Hanks"
RETURN p;
//Return nodes with label Movie, released property is between 1991 and
1999
MATCH (m:Movie)
WHERE m.released > 1990 AND m.released < 2000
RETURN m;

Extending the MATCH

//Find all the movies Tom Hanks is connected to
MATCH (:Person {name:"Tom Hanks"})--(m:Movie)
RETURN m.title;
Extending the MATCH

RETURN m.title;
//Find all the movies Tom Hanks directed and order by latest movie
MATCH (:Person {name:"Tom Hanks"})-[:DIRECTED]-(m:Movie)
RETURN m.title, m.released ORDER BY m.released DESC;
Extending the MATCH

RETURN m.title;
//Find all the movies Tom Hanks directed and order by latest movie
MATCH (:Person {name:"Tom Hanks"})-[:DIRECTED]-(m:Movie)
RETURN m.title, m.released ORDER BY m.released DESC;
//Find all of the co-actors Tom Hanks have worked with
MATCH (:Person {name:"Tom Hanks"})--(:Movie)-[:ACTED_IN]-(coActor:Person)
RETURN coActor.name;
Extending the MATCH

//Create a person node called "Tom Hanks"
CREATE (p:Person {name:"Tom Hanks"});
CREATE

//Create an ACTED_IN relationship between "Tom Hanks" and "Apollo 13"
MATCH (p:Person {name:"Tom Hanks"}), (m:Movie {title:"Apollo 13"})
CREATE (p)-[:ACTED_IN]->(m);
CREATE

//Create an ACTED_IN relationship between "Tom Hanks" and "Apollo 13"
MATCH (p:Person {name:"Tom Hanks"}), (m:Movie {title:"Apollo 13"})
CREATE (p)-[:ACTED_IN]->(m);
//Create the pattern of "Tom Hanks" ACTED_IN "Apollo 13"
//This will create the entire pattern, nodes and all!
CREATE (:Person {name:"Tom Hanks")-[:ACTED_IN]->(:Movie {title:"Apollo
13});
CREATE

Time to have a go!
We are going to:
• Go to dev.neo4j.com/aura-login
• Sign in & click “Create a database”
• Give your database a name
• Selected “Shared” database size
• Click “Create Database”
• Make a copy of the generated password - keep it safe!
Can’t access Aura Free? No problem! Use Neo4j Sandbox:
• Go to dev.neo4j.com/try
• Sign in & click “Blank sandbox”

So how do I continue my graph
journey?

More training this week - all starting at 1pm UTC
Thursday: Build APIs with Neo4j
GraphQL Library
Friday: Create a Knowledge Graph:
A Simple ML Approach
Tuesday: Hands-on with Neo4j
Aura Free Tier
Wednesday: Getting Started with
Neo4j Bloom
Read all about it!
https://dev.neo4j.com/training-week

Free online training and
certification:
• dev.neo4j.com/learn
How to, best practices, hands on
and community stories:
• dev.neo4j.com/videos
Come say hello :)
• dev.neo4j.com/chat
• dev.neo4j.com/forum
Continue your journey

Ljubica Lazarevic
Developer Relations
@ElLazal
lju@neo4j.com
Join the conversation at dev.neo4j.com/forum

Training Week: Introduction to Neo4j

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