Neo4j in 100 Seconds

Neo4j is an ACID-compliant graph database designed to handle extremely complex relational data of the modern world. Created in 2007 by Emil Eifrem, it is written in Java and pioneered the property graph model. Traditional relational databases use a tabular model, which doesn't align well with how humans naturally think about relationships. For example, we think of connections like "Bob asked a question on Stack Overflow, Alice and Chad downvoted it, so Bob gave up on his dream of programming." A graph can model this data the same way it might be visualized on a whiteboard: nodes represent entities, edges represent relationships between entities, and properties are key-value pairs that store data on these objects.

Under the hood, Neo4j is a true native graph database that applies this model down to the storage level. Queries are written in a declarative language called Cypher, which resembles SQL but has specific syntax for graph operations. For instance, nodes are surrounded by parentheses and connected to other nodes with arrows via relationships in brackets.

Today, Neo4j is used in applications like recommendation engines, social media platforms, and knowledge graphs for artificial intelligence, among others. You can get started with Neo4j by self-hosting it with Docker or opting for Neo4j Aura, a free fully-managed database in the cloud.

To begin, you can create nodes with the CREATE command in Cypher. Nodes can be labeled (e.g., User) and can have key-value properties. Relationships between nodes can be specified using arrows and brackets. Neo4j does away with foreign keys and join tables, but you can still enforce constraints, such as ensuring every username in your database is unique.

Cypher allows for complex querying, including filtering with WHERE clauses, matching string patterns, and applying regular expressions. You can also build more complex queries based on the graph's overall structure. For example, you might filter tweets to show only those from users who have not been muted.

Neo4j makes it intuitive for developers to interact with data while allowing natural patterns to emerge, which is advantageous for data analysis and machine learning.

Keywords

Neo4j
Graph Database
ACID-compliant
Property Graph Model
Cypher Query Language
Nodes
Relationships
Key-Value Pairs
Data Analysis
Machine Learning

FAQ

What is Neo4j?

Neo4j is an ACID-compliant graph database designed to handle complex relational data naturally through nodes, relationships, and properties.

Who created Neo4j?

Neo4j was created in 2007 by Emil Eifrem.

What language is Neo4j written in?

Neo4j is written in Java.

What query language does Neo4j use?

Neo4j uses a declarative query language called Cypher.

How does Neo4j represent data?

Neo4j represents data using nodes for entities, edges for relationships, and properties as key-value pairs.

Can Neo4j be self-hosted?

Yes, Neo4j can be self-hosted using Docker or run as a managed cloud service with Neo4j Aura.

What are some applications of Neo4j?

Neo4j is used in recommendation engines, social media platforms, and knowledge graphs for artificial intelligence.

How do you create a node in Cypher?

You can create a node using the CREATE command followed by parentheses, a label, and key-value pairs for properties.

Can Neo4j enforce constraints?

Yes, Neo4j can enforce constraints, such as ensuring each username in a database is unique.

How can you visualize data in Neo4j?

Data in Neo4j can be visualized as an interactive graph or even as a table.