Class Hierarchies with SQL

A standard DBMS stores information, such as objects, in the rows of the tables, conceived as set-theoretic relations in classical relational database systems. The relational database language SQL is used to define, populate, update, and query these kinds of databases. However, there are also simpler data storage techniques that don’t support SQL, but allow us to store data in table rows. For example, key-value storage systems, such as JavaScript’s Local Storage API, allow us to store a serialization of a JavaScript entity table as a key. This serialization, which is a map of entity records, is saved as a string value associated with the table name.

While there is no support for subtyping and inheritance in the classical version of SQL ...