Anything by Joe Celko: SQL for Smarties, Trees and Hierarchies in SQL for Smarties, Joe Celko Also, the internals of Django ORM (https://github.com/django/djan

Anything by Joe Celko: SQL for Smarties, Trees and Hierarchies in SQL for Smarties, Joe Celko Also, the internals of Django ORM (https://github.com/django/django/tree/2.2.5/django/db/models https://github.com/django/django/tree/2.2.5/django/db/models) and SQLAlchemy Core (https://github.com/sqlalchemy/sqlalchemy/tree/rel_1_3_8/lib/sqlalchemy/sql https://github.com/sqlalchemy/sqlalchemy/tree/rel_1_3_8/lib/...) and its dialects (https://github.com/sqlalchemy/sqlalchemy/tree/rel_1_3_8/lib/sqlalchemy/dialects https://github.com/sqlalchemy/sqlalchemy/tree/rel_1_3_8/lib/...) + ORM (https://github.com/sqlalchemy/sqlalchemy/tree/rel_1_3_8/lib/sqlalchemy/orm https://github.com/sqlalchemy/sqlalchemy/tree/rel_1_3_8/lib/...)