Cypher Query

Case sensitive

1. Node labels (:Person)
2. Relationship types (:ACTED_IN)
3. Property keys (name)

Case insensitive

1. Cypher keywords (MATCH, return)

Aggregate queries in Cypher are a little bit different than in SQL as we don't need to specify a grouping key.

We implicitly group by any non aggregate fields in the RETURN statement.

// implicitly groups by p.name
MATCH (p:Person)-[:ACTED_IN]->(m:Movie)
RETURN p.name, count(*) AS numberOfMovies

https://neo4j.com/docs/cypher-refcard/current/

We create unique constraints to:

1. ensure uniqueness
2. allow fast lookup of nodes which match label-property pairs.

CREATE CONSTRAINT ON (label:Label)
ASSERT label.property IS UNIQUE

There are three types of unique constraints:

1. Unique node property constraint
2. Node property existence constraint
3. Relationship property existence constraint

CREATE CONSTRAINT ON (label:Lable)
ASSERT EXISTS(label.name)

CREATE CONSTRAINT ON ()-[rel:REL_TYPE]->()
ASSERT EXISTS(rel.name)

We create indexes to:

1. allow fast lookup of nodes which match label-property pairs.

CREATE INDEX ON :Label(property)

The following predicates use indexes:

1. Equality
2. STARTS WITH
3. CONTAINS
4. ENDS WITH
5. Range searches
6. (Non-) existence checks

MERGE (p:Person {name:'Tom Hanks', oscar: true})
RETURN p

There is not a :Person node with name:'Tom Hanks' and oscar:true in the graph, but there is a :Person with name:'Tom Hanks'.

What do you think will happen here?

MERGE (p:Person {name:'Tom Hanks'})
SET p.oscar = true
RETURN p

CREATE (m:Movie {title:'Mystic River', released:2003})
RETURN m

MATCH (m:Movie {title:'Mystic River'})
SET m.tagline = 'We bury our sins here, Dave. We wash them clean.'
RETURN m

MATCH (m:Movie {title:'Mystic River'})
MATCH (p:Person {name:'Kevin Bacon'})
CREATE (p)-[r:ACTED_IN {role:['Sean']}]->(m)
RETRUN p,r,m

MERGE (p:Person {name: 'Your Name'})
ON CREATE SET p.created = timestamp(), p.updated= 0
On MATCH SET p.updated = p.updated + 1
RETURN p.created, p.updated

[USING PREIODIC COMMIT] // optional transaction batching
LOAD CSV // load csv data
WITH HEADERS // optionally use first header row as keys in 'row' map
FROM "url" // file:// URL relative to $NEO4J_HOME/import or http://
AS row // return each row of the CSV as list of strings or map
FIELDTERMINATOR ";" // alternative field delimiter

... rest of the Cypher statement ...

Type the following command into the query pane in the browser:

:play http://guides.neo4j.com/fundamentals/import.html

• Remote with Drivers
  • Bolt Binary Protocol
  • Officially Supported Drivers
  • Cypher transactional HTTP Endpoint
  • neo4j.com/developer/language-guides
• Native Java API
  • User Defined Procedures
  • Execute Cypher
  • Core Java API