11cGraphDBs
Database Management
11 May 2026
Intro
- One of the first kinds of databases was the network database
- It relaxed an assumption of the very first databases, which were strictly hierarchical
- Instead of every node having one parent (except the root), the network database node could have multiple parent-child relationships
- It fell out of favor when relational databases were introduced in the 1970s
- The network database was considered difficult to manage in comparison to the relational model
- But it served an important purpose and has been reborn in a sense in contemporary graph databases
The graph database
- Graph theory is a branch of mathematics that works with sets of objects called nodes (also known as vertices or locations) and edges (also known as arcs or links)
- Graph theory enjoyed a surge in popularity when social networks on the web became popular and it was found that social networks obeyed certain laws of graph theory
- But representing social networks was problematic with existing databases
- Hence, graph databases have become fairly popular for representing relationships between things
Popular uses of graph databases
According to Gemini:
- Social Networks: Mapping connections (friends, followers)
- Fraud Detection: Identifying complex, hidden patterns in financial transactions
- Recommendation Engines: Real-time product or content recommendations based on user behavior
- Knowledge Graphs: Powering AI systems and search engines (e.g., using Graph RAG)
- Network & IT Operations: Mapping infrastructure dependencies.
Example: Neo4j
- Neo4j is the most popular graph database product
- Represents three basic concepts
- nodes (things, people)
- edges (relationships)
- properties (key-value pairs attached to nodes or edges)
- Uses the Cypher Query Language to manage databases
Cypher Query Language
- Similar to SQL except it models relationships and properties
- Uses a
MATCHkeyword to match patterns in the graph
- Contains a
WHEREclause to define conditions
- Uses a
RETURNclause to organize output of a query
- In the following example, the keywords begin each line, all other words are user defined
- In the following example, the punctuation is vital to specifying the patterns
Wikipedia example of a Cypher query
A visual graph produced by Neo4j
Further reading
- I taught a class in Contemporary Databases a decade ago and wrote a hundred page study guide for it, mostly focused on MongoDB and Neo4j. That book is in Canvas > Files > contemporaryDatabases.pdf.
- I made extensive use of Robinson et al. (2015) in that class, and recommend it if you want to learn more about Neo4j.
END
References
Robinson, Ian, Jim Webber, and Emil Eifrem. 2015. Graph Databases, 2nd Edition. O’Reilly Media.
Colophon
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