Victoria Holt has some good resources on learning more about graph databases:
There is graph support in the next version of SQL Server. The private preview page states
SQL Graph adds graph processing capabilities to SQL Server, which will help you link different pieces of connected data to help gather powerful insights and increase operational agility. Graphs are well suited for applications where relationships are important, such as fraud detection, risk management, social networks, recommendation engines, predictive analysis, dependence analysis, IoT suites, etc.
Initially, SQL Server will support CRUD graph operations and multi-hop graph navigation, and the following functionality will be available in the private preview:
- Create graph objects, that is, nodes to represent entities and edges to represent relationships between any 2 given nodes. Both Nodes and Edges can have properties associated to them.
- SQL language extensions to support join free, pattern matching queries for multi-hop navigation
Kennie Pontoppipidan wrote a great blog post on where to find out more information.
Click through for more links to interesting resources.