Difference between revisions of "Neo4j:Basics - Introduction"

Working with the greek_gods family tree graph

This tutorial introduces NoSQL using Neo4j. We will be using the RETURN, MATCH, and WHERE commands on the greek_gods collection which contains a family tree of around 130 individuals.

For anyone wishing to use this data-set on their own machines, the Cypher file used to build it is available here: *TBA*.

Introduction to Graphs and the 'Graph Property Model'

You've likely heard of graphs before. In mathematics a graph is the term for a set of vertices and edges, here the terms nodes and relationships are used instead.

In Neo4j graphs follow the "Property Graph Model". A property is just a key-value pair, such as name: 'Alice' or age: 27. Users who have used document-oriented databases such as MongoDB will find this concept very similar.

A node is a simple entity that contains any amount of properties, and they can be labeled as belonging to a certain set. For example, in a database of celebrities Stephen Fry could be labeled as a :Actor. There's no limit to the amount of labels that can apply to a node, the celebrity Hugh Laurie could be simultaneously labeled as an :Actor, :Musician, and :Author.

In the property graph model, a relationship is a connection between exactly two nodes, though there's not limit to the amount of relationships a node made have. A relationship always has both a name and a direction (start node and end node), and like a node it can also have properties. Bidirectional relationships are a little trickier, and are out-width the scope of this tutorial: Modelling Bidirectional Relationships

This remainder of this tutorial will use the Cypher query language to introduce some basic concepts.

RETURN

RETURN 2 + 2, "A" + "B", [1, 2, 3] + [4];

MATCH and WHERE

MATCH (n)
WHERE n:God AND n.name = 'Zeus'
RETURN n;

MATCH (g) WHERE g:God AND g.name = 'Zeus' RETURN g; 

MATCH (g:God {name: 'Zeus'})
RETURN g;

MATCH (g:God {name: "Zeus"}) 
RETURN g.name, g.greek;

MATCH (g:God {name: "Zeus"}) RETURN g.name, g.greek;

MATCH (g:God) 
WHERE g.name IN ['Hera', 'Demeter'] 
RETURN g.name, g.greek;

MATCH (g:God) WHERE g.name IN ['Zeus', 'Poseidon', 'Hades'] RETURN g.name, g.greek;

MATCH (o:Olympian)
RETURN o.name;

MATCH (o:Olympian) WHERE NOT o.name IN ['Apollo', 'Hestia'] RETURN o.name;

Further examples can be found here: MATCH Examples.
Once comfortable with these questions, move onto MATCH Basics - Relationships.