Purpose
Many of our projects use relational databases.
Learning Material
Basics
The PostgreSQL Tutorial provides a nice introduction to SQL and to Postgres. Sections 3.5 and 3.6 are less relevant.
The Django Documentation about Models provides a nice description of how the Django ORM relates to the underlying database.
Further Learning
This Stanford Course is a great place to learn databases in-depth, including the mathematical foundations of relational databases. There is too much information here for practical day-to-day usage, but if you have time time and inclination, this course lays a great foundation. Articles that provide a conceptual basis for how CSS works:
Exercises
No problems are written for this lesson yet.