What is Neo4j?
The traditional database is called a “relational database,” yet it isn’t all that good at expressing relations. Neo4j takes the “graph database” approach, which puts relations at the heart of everything. This makes it a better choice for some software applications.
The term “graph database” doesn’t mean what it sounds like. It has nothing to do with drawing charts (though it could hold chart data). “Graph” is a bit of computer jargon that means a set of connections among data points. Think of an organization chart, with all its connecting lines among people. That’s the kind of graph we’re talking about.
A relational database is built out of tables; it can use some of the information in a table to look up information in another table. Finding relationships is a laborious process, often requiring strange and complex SQL code. With graph databases, relations are explicit instead of requiring a lookup.
Graph databases work best when chains of connection among data, such as “friend of a friend” relationships, are important. For applications that emphasize tables, such as lists of customers with contact information, a traditional relational database may be better.
Neo4j is one of the most widely used graph databases. It uses a query language called Cypher, which looks a lot like SQL. The e-book Learning Neo4j allows developers to learn how to use it, and Manning’s Neo4j in Action is available in both print and e-book form.
Neo4j is available in a Community Edition and an Enterprise Edition. The Community Edition uses the GPL software license, which is free but requires that published software using it also be free. Using it for closed-source applications requires a commercial license. The Enterprise Edition is also available under an educational license.
It runs on Linux, HP-UX, and Windows Server 2012. System requirements call for Java 7 or 8, with version 8 preferred, and recommend at least 16 gigabytes of memory.
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