memgraph/docs/user_technical/examples.md

Examples

This chapter shows you how to use Memgraph on real-world data and how to get interesting and useful information out of it.

TED Talks Example

TED is a nonprofit organization devoted to spreading ideas, usually in the form of short, powerful talks. Today, TED talks are influential videos from expert speakers on almost all topics — from science to business to global issues. Here we present a small dataset which consists of 97 talks. We'll show you how to model this data as a graph and demonstrate a few example queries.

Data Model

Each TED talk has a main speaker, so we identify two types of nodes — Talk and Speaker. Also, we will add an edge of type Gave pointing to a Talk from its main Speaker. Each speaker has a name so we can add property name to Speaker node. Likewise, we'll add properties name, title and description to node Talk. Furthermore, each talk is given in a specific TED event, so we can create node Event with property name and relationship InEvent between talk and event.

Talks are tagged with keywords to facilitate searching, hence we add node Tag with property name and relationship HasTag between talk and tag. Moreover, users give ratings to each talk by selecting up to three predefined string values. Therefore we add node Rating with these values as property name and relationship HasRating with property user_count between talk and rating nodes.

Example Queries

We have prepared a database snapshot for this example, so you can easily import it when starting Memgraph using the --durability-directory option.

/usr/lib/memgraph/memgraph --durability-directory /usr/share/memgraph/examples/TEDTalk \
  --durability-enabled=false --snapshot-on-exit=false

When using Memgraph installed from DEB package, you may need to stop the currently running Memgraph server before you can import the example. Use the following command:

systemctl stop memgraph

When using Docker, you can import the example with the following command:

docker run -p 7687:7687 \
  -v mg_lib:/var/lib/memgraph -v mg_log:/var/log/memgraph -v mg_etc:/etc/memgraph \
  memgraph --durability-directory /usr/share/memgraph/examples/TEDTalk \
  --durability-enabled=false --snapshot-on-exit=false

Now you're ready to try out some of the following queries.

NOTE: If you modify the dataset, the changes will stay only during this run of Memgraph.

1. Find all talks given by specific speaker:

MATCH (n:Speaker {name: "Hans Rosling"})-[:Gave]->(m:Talk)
RETURN m.title;

2. Find the top 20 speakers with most talks given:

MATCH (n:Speaker)-[:Gave]->(m)
RETURN n.name, COUNT(m) as TalksGiven
ORDER BY TalksGiven DESC LIMIT 20;

3. Find talks related by tag to specific talk and count them:

MATCH (n:Talk {name: "Michael Green: Why we should build wooden skyscrapers"})-[:HasTag]->(t:Tag)<-[:HasTag]-(m:Talk)
WITH * ORDER BY m.name
RETURN t.name, COLLECT(m.name), COUNT(m) AS TalksCount
ORDER BY TalksCount DESC;

4. Find 20 most frequently used tags:

MATCH (t:Tag)<-[:HasTag]-(n:Talk)
RETURN t.name as Tag, COUNT(n) AS TalksCount
ORDER BY TalksCount DESC, Tag LIMIT 20;

5. Find 20 talks most rated as "Funny". If you want to query by other ratings, possible values are: Obnoxious, Jaw-dropping, OK, Persuasive, Beautiful, Confusing, Longwinded, Unconvincing, Fascinating, Ingenious, Courageous, Funny, Informative and Inspiring.

MATCH (r:Rating{name:"Funny"})<-[e:HasRating]-(m:Talk)
RETURN m.name, e.user_count ORDER BY e.user_count DESC LIMIT 20;

6. Find inspiring talks and their speakers from the field of technology:

MATCH (n:Talk)-[:HasTag]->(m:Tag {name: "technology"})
MATCH (n)-[r:HasRating]->(p:Rating {name: "Inspiring"})
MATCH (n)<-[:Gave]-(s:Speaker)
WHERE r.user_count > 1000
RETURN n.title, s.name, r.user_count ORDER BY r.user_count DESC;

7. Now let's see one real-world example — how to make a real-time recommendation. If you've just watched a talk from a certain speaker(e.g. Hans Rosling) you might be interested in finding more talks from the same speaker on a similar topic:

MATCH (n:Speaker {name: "Hans Rosling"})-[:Gave]->(m:Talk)
MATCH (t:Talk {title: "New insights on poverty"})-[:HasTag]->(tag:Tag)<-[:HasTag]-(m)
WITH * ORDER BY tag.name
RETURN m.title as Title, COLLECT(tag.name), COUNT(tag) as TagCount
ORDER BY TagCount DESC, Title;

The following few queries are focused on extracting information about TED events.

8. Find how many talks were given per event:

MATCH (n:Event)<-[:InEvent]-(t:Talk)
RETURN n.name as Event, COUNT(t) AS TalksCount
ORDER BY TalksCount DESC, Event
LIMIT 20;

9. Find the most popular tags in the specific event:

MATCH (n:Event {name:"TED2006"})<-[:InEvent]-(t:Talk)-[:HasTag]->(tag:Tag)
RETURN tag.name as Tag, COUNT(t) AS TalksCount
ORDER BY TalksCount DESC, Tag
LIMIT 20;

10. Discover which speakers participated in more than 2 events:

MATCH (n:Speaker)-[:Gave]->(t:Talk)-[:InEvent]->(e:Event)
WITH n, COUNT(e) AS EventsCount WHERE EventsCount > 2
RETURN n.name as Speaker, EventsCount
ORDER BY EventsCount DESC, Speaker;

11. For each speaker search for other speakers that participated in same events:

MATCH (n:Speaker)-[:Gave]->()-[:InEvent]->(e:Event)<-[:InEvent]-()<-[:Gave]-(m:Speaker)
WHERE n.name != m.name
WITH DISTINCT n, m ORDER BY m.name
RETURN n.name AS Speaker, COLLECT(m.name) AS Others
ORDER BY Speaker;

Now you're ready to explore the world of graph databases with Memgraph by yourself and try it on many more examples and datasets.

Graph Gists Examples

A nice looking set of small graph examples can be found here. You can take any use-case and try to execute the queries against Memgraph. To clear the database between trying out examples, execute the query:

MATCH (n) DETACH DELETE n;