Django models describe the data an application stores and the relationships between records. They also give the ORM a Python interface for creating and querying those records. Understanding the layers helps developers avoid treating a model class as if it were the database itself.
Define models around domain records
A model field maps to a stored value, while relationship fields describe how records connect. A foreign key is a common way to represent a many-to-one relationship. Add constraints when a rule, such as a unique slug, must hold for all writes.
Use migrations to evolve the schema
When a model changes, Django can create a migration that records the schema operation. Review generated migrations before applying them, especially when a change affects existing data. In production, deploy code and migrations deliberately; do not delete or recreate a database to resolve a pending migration.
Keep ORM queries explicit
Filters, ordering, and relationship loading determine what the application asks PostgreSQL to return. Use select_related for suitable single-valued relationships and prefetch_related for collections when that avoids repeated queries. Confirm behavior with tests and query inspection instead of guessing.
active_tasks = Task.objects.filter(
project__owner=request.user,
is_complete=False,
).select_related("project")Models, migrations, and querysets work best when they match clear domain rules. Keep request validation in the form or serializer, persistence in the model/database layer, and presentation in the template or response.