📄️ Relational Databases: How Structured Data Works
Understand what relational databases are, why structure and relationships matter, and when to choose SQL over NoSQL. The foundation for everything in this module.
📄️ SQL Basics: Reading Data with SELECT
Write your first SQL queries using SELECT, FROM, WHERE, ORDER BY, and LIMIT. Learn declarative thinking and start pulling real data from the ShopFlow tables.
📄️ SQL Aggregations: Summarizing Data
Use COUNT, SUM, AVG, MIN, and MAX to summarize data. Learn GROUP BY to split results into categories and HAVING to filter aggregated groups — and understand why WHERE can't do that job.
📄️ SQL Joins: Combining Tables
Learn how to query across multiple tables using INNER JOIN, LEFT JOIN, and self-joins. Understand why joins work, how the cartesian product danger appears, and how to build the ShopFlow order summary query.
📄️ SQL Writes: INSERT, UPDATE, DELETE
Add, modify, and remove data in PostgreSQL using INSERT, UPDATE, and DELETE. Learn why UPDATE without WHERE is dangerous, how to preview destructive operations, and how BEGIN/COMMIT/ROLLBACK keep your data safe.