Neo4j

Neo4j is a graph database platform that simplifies operations and analysis on network graphs. It is designed for fast management of nodes and relationships and is significantly faster than performing JOINS on tables.

Neo4j Cypher

Cypher is Neo4j's query language. It is built for working with graph data and uses patterns to match and describe graph data. Example of a Neo4j query:

Node syntax in Cypher

() represents an anonymous node. If we want to refer to the node elsewhere, we add a varriable, like (matrix).
() - anonymous node
(matrix) - variable added to node. This variable can be referenced later in the query
(:Movie) - label :Movie declares the node's type
(matrix:Movie) - variable name matrix with label Movie
(matrix:Movie {title: "The Matrix"}) - variable matrix of type Movie with the property title having value 'The Matrix'
(matrix:Movie {title: "The Matrix", released: 1997})
Variables are restricted to single statement i.e they may have different or no meaning in another statement

Pattern Syntax

Example:
(:Person) - [:LIVES_IN]->(:CITY)-[:PART_OF]->(:Country)
This statement finds a Person (label) who "Lives in" (relationship) in a "City" (label) which is "Part Of" (relationship) a "country" (label)

Pattern Syntax with variables

Using a variable is useful if one wants to refer to that variable later on in a query. IF we are matching a label, we may just specify any variable name before the colon as shown below:

MERGE (a:Person {name:"Ann"})
CREATE (a)-["HAS_PET]->(:Dog{name:"Sam"})

The above query Creates a relationship with the Dog whose name is Sam. The person is stored as a and a is referred to when creating the node and relationship with Ann's pet.