I'm adding a table and subclass table to my DB. (Subclass table = table where the primary key joins to the primary key of another table, to give extra row information to some subset of the rows.

MySQL is changing the way foreign key constraints and cascades are managed. Starting with MySQL 9.6, foreign key validation and cascade actions are handled by the SQL layer rather than the InnoDB ...

SQL Server's OpenJson function will let you dismantle JSON structures into relational tables, including tables with foreign/primary key relationships. As I noted in an earlier column, JSON is great ...