SQL & Relational Databases
Start with tables, keys, joins, filters, indexes, and transactions. The course teaches query behavior before pushing you into larger problems.
Open the course →Data & SQL
Learn SQL by reasoning about rows, not memorizing syntax.
Build the mental model first, then use focused problems to predict results, write a query, inspect alternatives, and understand the performance trade-offs.
2 deep SQL problems
Each problem includes schema and sample data, expected output, a hint, a primary solution, alternatives, common mistakes, and performance notes.
Browse SQL problems →