Designing ORM-friendly classes

When using an ORM, we will fundamentally change the way we design and implement our persistent classes. We're going to expand the semantics of our class definitions to have the following three distinct levels of meaning:

  • The class will be used to create Python objects. The method functions are used by these objects.
  • The class will also describe an SQL table and can be used by the ORM to create the SQL DDL that builds and maintains the database structure. The attributes will be mapped to SQL columns.
  • The class will also define the mappings between the SQL table and Python class. It will be the vehicle to turn Python operations into SQL DML and build Python objects from SQL query results.

Most ORMs are designed ...

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