[galaxyLogic]

It might be just a good way of thinking about it. In practice it might provide some ideas about how to translate between an Object-view and Relational-View.

What I'd like to find is a relational database where field-values can be not just elementary values like numbers and strings but also "object-instances".

I wonder is there such a database? It would seem to offer the best of both worlds, objects, and relations between objects.

[ynniv]

GemStone is a common one, but object databases are not very common due to the maturity, efficiency, and predictability of relational databases. The deep pipelining and caching models of CPUs are a better match for RDBMs than object ones.

https://en.wikipedia.org/wiki/Gemstone_(database)

[galaxyLogic]

I understand that Gemstone is an Object-Oriented Database that stores objects and is great at that. But can you query those objects with SQL?

What I'd like to understand is, is there some basic reason why RDBMS and ODBMs must be different databases. Or could their conceptual models of data perhaps be generalized into a single model. Using hyper-graphs perhaps. :-)

[nighthawk454]

This might not be quite it, but perhaps you’re looking for graph databases?

[galaxyLogic]

Can you use SQL with graph databases?

Related to the current topic, do graph databases support hyper-graphs?

[nighthawk454]

I don't believe they support SQL. They're somewhat more like pattern-matching on graphs. Most of their query language pages have compare/contrast examples with an equivalent SQL query. e.g. Neo4j's Cypher query language [1], or Apache Tinkerpop Gremlin (seriously) [2] used by Amazon Neptune.

I don't think the most popular ones support hypergraphs, although that sounds cool. I did see HypergraphDB [3] though! Need to read more about that.

[1] https://neo4j.com/developer/cypher/guide-sql-to-cypher/#cyph... [2] https://tinkerpop.apache.org/gremlin.html#:~:text=Host%20Lan... [3] http://hypergraphdb.org/