30-Day SQL Program for Data Engineers Targeting FAANG Interviews (Free Resources)

This 30-day roadmap is designed for data engineers preparing for FAANG interviews, leveraging only free, high-quality resources. The plan is structured to build foundational knowledge, advance to complex queries, and master real interview problems, with daily practice and review.

Week 1: SQL Fundamentals

Day 1-2: Introduction to SQL, Database Concepts

  • Learn about RDBMS, tables, and basic SQL structure
  • Resource: SQLBolt (Lessons 1-3)

Day 3-4: Basic SQL Commands

  • SELECT, WHERE, ORDER BY, LIMIT
  • Resource: SQLBolt (Lessons 4-6), DataLemur’s 30-Day Roadmap5

Day 5: Filtering and Sorting

  • Practice filtering with WHERE, sorting with ORDER BY
  • Resource: DataLemur SQL Tutorials5

Day 6-7: Working with Multiple Tables

  • Understanding JOINs (INNER, LEFT, RIGHT, FULL)
  • Resource: SQLBolt (Lessons 7-9), DataLemur5

Week 2: Aggregations and Intermediate Queries

Day 8-9: Aggregations

  • COUNT, SUM, AVG, MIN, MAX, GROUP BY, HAVING
  • Resource: Mode Analytics SQL Tutorial, DataLemur5

Day 10: Subqueries

  • Writing and using subqueries in SELECT, FROM, WHERE
  • Resource: SQLBolt (Lesson 13), DataLemur5

Day 11-12: Real-World Problem Solving

  • Solve basic SQL problems
  • Resource: DataLemur, StrataScratch25

Day 13-14: SQL Execution Order & Query Optimization Basics

  • Learn SQL execution order, basic optimization tips
  • Resource: DataLemur Interview Guide15

Week 3: Advanced SQL Concepts

Day 15-16: Window Functions

  • ROW_NUMBER, RANK, DENSE_RANK, LEAD, LAG
  • Resource: Mode Analytics, DataLemur5

Day 17-18: Common Table Expressions (CTEs)

  • Syntax and use cases for CTEs
  • Resource: DataLemur, SQLBolt (Lesson 14)5

Day 19: CASE Statements and Conditional Logic

  • Using CASE for conditional queries
  • Resource: DataLemur, SQLBolt5

Day 20: Advanced Filtering, Nested Queries

  • Practice advanced WHERE, HAVING, and nested queries
  • Resource: DataLemur, StrataScratch25

Day 21: Practice: Intermediate SQL Problems

  • Solve intermediate SQL interview questions
  • Resource: DataLemur, StrataScratch25

Week 4: Performance, Design, and Interview Prep

Day 22: Indexes and Performance Optimization

  • Index basics, query optimization strategies
  • Resource: DataLemur, LinkedIn Roadmap45

Day 23: Stored Procedures and Functions

  • Writing and using stored procedures/functions
  • Resource: DataLemur, LinkedIn Roadmap45

Day 24: Transactions and Error Handling

  • ACID properties, BEGIN/COMMIT/ROLLBACK
  • Resource: DataLemur, LinkedIn Roadmap45

Day 25: Data Modeling & Schema Design

  • Understanding normalization, denormalization, keys
  • Resource: DataLemur, DataEngineerAcademy35

Day 26-27: Advanced SQL Problems

  • Tackle FAANG-level SQL interview questions (complex joins, window functions, analytics)
  • Resource: DataLemur FAANG SQL Problems, StrataScratch, DataEngineerAcademy35

Day 28: System Design for Data Engineers

  • Practice explaining schema and data pipeline designs
  • Resource: DataEngineerAcademy, DataLemur Interview Guide13

Day 29: Mock Interviews & Whiteboard Practice

  • Simulate interviews, write queries by hand
  • Resource: DataLemur, StrataScratch, LinkedIn Roadmap1245

Day 30: Portfolio Project & Review

  • Build a small project (e.g., analytics dashboard or ETL pipeline using SQL)
  • Review mistakes, revisit weak areas
  • Resource: DataLemur, SQLBolt, Mode Analytics5

Key Free Resources

ResourceUse Case
SQLBoltInteractive SQL basics
DataLemurTutorials, interview questions
StrataScratchReal interview problems
Mode AnalyticsIntermediate/advanced SQL
DataEngineerAcademyFAANG-specific SQL prep
LinkedIn RoadmapStructured daily learning

Tips for Success

  • Practice daily: Consistency is crucial.
  • Solve real interview questions: Focus on FAANG-style problems35.
  • Explain your logic: Practice verbalizing your thought process12.
  • Simulate interviews: Use whiteboard or online tools for mock interviews25.
  • Review and reflect: Spend time on mistakes and revisit tough concepts45.

This roadmap, if followed with discipline and curiosity, will prepare you for the SQL portion of any FAANG data engineering interview using only free, high-impact resources135.

  1. https://datalemur.com/blog/sql-interview-guide
  2. https://www.stratascratch.com/blog/sql-interview-questions-you-must-prepare-the-ultimate-guide/
  3. https://dataengineeracademy.com/blog/faang-interviews-prep/
  4. https://www.linkedin.com/pulse/30-day-roadmap-learn-sql-data-analysis-suraj-kumar-soni-9pohc
  5. https://datalemur.com/blog/learn-sql-in-30-days-roadmap
  6. https://www.datacamp.com/blog/top-sql-interview-questions-and-answers-for-beginners-and-intermediate-practitioners
  7. https://www.reddit.com/r/SQL/comments/12nzhwm/best_free_platform_to_practice_hard_sql_questions/
  8. https://www.datacamp.com/blog/top-21-data-engineering-interview-questions-and-answers
  9. https://www.nicksingh.com/posts/30-sql-and-database-design-questions-from-real-data-science-interviews
  10. https://www.stratascratch.com/blog/data-science-sql-interview-questions-from-faang-companies/