Lesson 1: Tables, keys and queries that stay fast
19 min read·13 Oct 2026
Module 11 · Lesson 1 · About 45 minutes · Needs: Module 2, Lesson 1 (joins and grouping in pandas)
The situation
BrightCart's data still lives in Python dictionaries that vanish when the notebook stops. The assistant needs a permanent store, and two people already have questions for it. Priya wants tickets per category and the customers who have never written in. Marta wants each customer's orders with totals.
You build that store in SQLite, the database that ships inside Python (sqlite3), so it runs in Colab with nothing to install. The SQL carries over to PostgreSQL, which Lesson 2 sets up for the real service; where the two differ, this lesson says so.