JugMarche: Neo4j 2 (Cypher)
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This document summarizes a presentation about Neo4j and Cypher. It introduces Neo4j as a graph database that supports ACID transactions and can be run embedded or on a server. It describes how Neo4j models data as nodes and relationships and supports optional schemas. It provides examples of querying Neo4j with both the REST API and the Cypher query language, demonstrating commands like MATCH, MERGE, OPTIONAL MATCH, and aggregations. It also discusses more advanced Cypher features and taking questions.
![Querying: REST API
Properties of node with id 32:
GET http://localhost:7474/db/data/node/32/properties
{
"user": "@onof80",
"lastLogin": 1394304000,
"tags": ["Java","Scala","NoSql"]
}](https://image.slidesharecdn.com/2014-06neo4j-140623012307-phpapp02/85/JugMarche-Neo4j-2-Cypher-6-320.jpg)
![Traversing the graph
for ( Path position : db.traversalDescription()
.depthFirst()
.relationships( Rels.KNOWS, Direction.INCOMING )
.evaluator( Evaluators.toDepth( 5 ) )
.traverse( node6 ) )
{
output += position + "n";
}
(6)
(6)<--[KNOWS,1]--(3)
(6)<--[KNOWS,1]--(3)<--[KNOWS,6]--(0)
(6)<--[KNOWS,1]--(3)<--[KNOWS,6]--(0)<--[KNOWS,4]--(5)
Powerful but
hardcoded](https://image.slidesharecdn.com/2014-06neo4j-140623012307-phpapp02/85/JugMarche-Neo4j-2-Cypher-7-320.jpg)
![Querying with Cypher
START n=node(10)
MATCH path =(n)<-[:KNOWS*0..5]-()
RETURN path
http://console.neo4j.org/](https://image.slidesharecdn.com/2014-06neo4j-140623012307-phpapp02/85/JugMarche-Neo4j-2-Cypher-8-320.jpg)
![Create a full path
CREATE (a:Language { name: "Java"}),
(b:Language { name: "Scala" }),
(c:Language { name: "JavaScript" }),
(jvm:Platfom { name: "JVM" }),
path=(a)-[r:RUNS_ON]->(jvm)
<-[r2:RUNS_ON]-(b)
RETURN path](https://image.slidesharecdn.com/2014-06neo4j-140623012307-phpapp02/85/JugMarche-Neo4j-2-Cypher-9-320.jpg)
![Optional paths
MATCH (a:Language)
OPTIONAL MATCH (a)-[:RUNS_ON]-(b)
RETURN a,b
ORDER BY a.name](https://image.slidesharecdn.com/2014-06neo4j-140623012307-phpapp02/85/JugMarche-Neo4j-2-Cypher-13-320.jpg)
![Aggregations
MATCH (a:Language)
OPTIONAL
MATCH (a)-[:RUNS_ON]-(b)
RETURN b.name, COUNT(*)](https://image.slidesharecdn.com/2014-06neo4j-140623012307-phpapp02/85/JugMarche-Neo4j-2-Cypher-14-320.jpg)
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JugMarche: Neo4j 2 (Cypher)
- 1. Neo4j 2: Learning Cypher JUG Marche - June 2014 Onofrio Panzarino
- 2. Graph databases and me ● RDF (Semantic web) ○ 2004-2005: Sesame (SPARQL) ● Neo4j ○ 2011: Java API (Embedded), Traversers ○ 2013: Cypher Twitter: @onof80 Blog: http://learningcypher.blogspot.com My book: Learning Cypher
- 3. What is Neo4j - Graph database - ACID transaction - 2 running modes > Embedded (JAVA API) > Server (REST) - Cypher Query Language
- 4. Model: nodes and relationships Source: http://gist.neo4j.org/?8635758
- 5. Schema? Schemaless (key- value) Nodes: > properties Relationships: > properties Schema Nodes: 0+ Labels Relationships: 1 Type Indexes+Constraints
- 6. Querying: REST API Properties of node with id 32: GET http://localhost:7474/db/data/node/32/properties { "user": "@onof80", "lastLogin": 1394304000, "tags": ["Java","Scala","NoSql"] }
- 7. Traversing the graph for ( Path position : db.traversalDescription() .depthFirst() .relationships( Rels.KNOWS, Direction.INCOMING ) .evaluator( Evaluators.toDepth( 5 ) ) .traverse( node6 ) ) { output += position + "n"; } (6) (6)<--[KNOWS,1]--(3) (6)<--[KNOWS,1]--(3)<--[KNOWS,6]--(0) (6)<--[KNOWS,1]--(3)<--[KNOWS,6]--(0)<--[KNOWS,4]--(5) Powerful but hardcoded
- 8. Querying with Cypher START n=node(10) MATCH path =(n)<-[:KNOWS*0..5]-() RETURN path http://console.neo4j.org/
- 9. Create a full path CREATE (a:Language { name: "Java"}), (b:Language { name: "Scala" }), (c:Language { name: "JavaScript" }), (jvm:Platfom { name: "JVM" }), path=(a)-[r:RUNS_ON]->(jvm) <-[r2:RUNS_ON]-(b) RETURN path
- 10. MERGE Look for a pattern: ● Found? Match it ● Else create it MERGE (a:Language { name: "Java" }) SET a.version = 8 RETURN a
- 11. Idempotent operations MATCH (a:Language) REMOVE a.version MATCH (a:Language) DELETE a
- 12. But... MERGE (a:Language { name: "Java" }) ON MATCH SET a.version = a.version + 1 ON CREATE SET a.version = 1 RETURN a
- 13. Optional paths MATCH (a:Language) OPTIONAL MATCH (a)-[:RUNS_ON]-(b) RETURN a,b ORDER BY a.name
- 14. Aggregations MATCH (a:Language) OPTIONAL MATCH (a)-[:RUNS_ON]-(b) RETURN b.name, COUNT(*)
- 15. Other keywords Splitting queries WITH Manipulating collections EXTRACT, FILTER, REDUCE Predicates ALL, ANY, SINGLE, NONE
- 16. More features Integration LOAD CSV WITH HEADERS FROM <file> AS line CREATE ... Profiling PROFILE <query>
- 18. Any questions? Q&A More infos: http://docs.neo4j.org/ My book All Neo4j books