SQL for Data & Backend Interviews: Queries You Must Know
JOINs, window functions, CTEs, indexing strategy, and query optimization — with real interview questions from Meta, Amazon, and fintech companies. Must-know concepts. SQL appears in data analyst, backend, and full-stack loops. Interviewers test JOIN logic, aggregation, window functions, and whether you understand indexes — not obscure syntax trivia. Classic interview question. "Find users who made a purchase in January but not February" — tests LEFT JOIN with NULL check or NOT EXISTS. Always clarify NULL handling and duplicate rows.