SQL Interview Prep | Core to MAANG Level

Stop Googling random SQL questions. Start practicing the patterns interviewers actually test.

This is a structured, progressive collection of 98 SQL problems — from fundamentals to MAANG-level classics — designed specifically for Data Engineer, Data Analyst, and Backend Developer interviews.

What's inside (3 PDFs):

Level 1 — Core Concepts (38 Problems)

1. SELECT, WHERE, ORDER BY, GROUP BY, HAVING
2. All JOIN types (INNER, LEFT, RIGHT, FULL, CROSS, SELF)
3. Preventing join explosions & understanding cardinality
4. Subqueries (correlated, non-correlated, EXISTS, IN)
5. Set operations (UNION, INTERSECT, EXCEPT)
6. NULL handling traps that catch 90% of candidates
7. String, Date, and Type Conversion functions

Level 2 — Advanced Concepts (40 Problems)

1. Window Functions: ROW_NUMBER, RANK, DENSE_RANK, LAG, LEAD, NTILE
2. Moving averages, running totals, YTD calculations
3. Data Engineering: MERGE/UPSERT, SCD Type 2, incremental loads
4. CTEs, Recursive CTEs, PIVOT/UNPIVOT, ROLLUP, LATERAL JOIN
5. 10 MAANG Classics: Second Highest Salary, Consecutive Logins, Retention Analysis, Funnel Conversion, DAU/WAU/MAU

Level 3 — Functions & Performance (20 Problems)

1. String/Date/Math functions for data cleaning
2. Indexes, EXPLAIN ANALYZE, Partitioning
3. Performance anti-patterns (and how to fix them)
4. Distributed joins (Broadcast vs Shuffle)
5. GROUPING SETS, CUBE, STRING_AGG
6. Transactions, Views, Materialized Views
7. More MAANG: Leetcode 185, 262, 603

Format: Every problem includes → Input Table → Expected Output → Explanation → Solution. No fluff. Just problems you can practice and patterns you can memorize.

Who this is for:

1. Preparing for Data Engineer / Analyst interviews
2. Targeting MAANG, startups, or any company that tests SQL
3. Want a searchable, offline-ready reference (not a 10-hour video course)