Modules 1 & 1B: SQL

This PSET covers SQL: SELECT/WHERE, joins, NULL three-valued logic, GROUP BY and HAVING, set operations, and subqueries, plus CTEs and window functions from Module 1B. It opens with concept checks, then two query-reasoning scenarios (one query shown once, several questions each) and a set of query- and output-equivalence problems. Before starting, you should have read the Module 1 content, attended the lectures, and completed the matching Colab walkthrough in your CA section.