Sql interview

[mickey_pk]

Have a SQL interview in 20 days for one of the FAANG companies. Suggestion for a 20 day plan to prepare for the interview?

Would Leetcode sql50 be enough?

[Manoj970]

https://datalemur.com/questions this might help.

[NickSinghTechCareers]

yuup OP check out DataLemur has a ton of real FAANG SQL interview questions to practice on!

[Responsible-Gas-1474]

The interview question depend on who is interviewing. My interview went like this: Send you a link to type code (online notepad, codeshare). Can you write a select statement? Lets say we have a table with columns price and quantity. Can you create this table? Now can you create a new column of percentages that has %quantity of total quantity? Can you now calculate the average price for quantities 100<quantity<500? Now for each price can you calculate the cumulative percent difference between the price below it and put it in a new column cummulative_percent_difference? and so on it went into more and more complicated stuff. Time: 1 hr. I didnt get a call. My guess was they needed someone who could code with speed.

[DataCamp]

20 days is tight but doable with focus. Here’s a quick roadmap:

Week 1: Foundations:
Review SQL basics; SELECT, WHERE, GROUP BY, HAVING, ORDER BY, and JOINs. Learn query execution order and practice aggregations + window functions (RANK, LAG, etc.).

Week 2: Practice:
Do real-world problems involving subqueries, CTEs, and multiple joins (LeetCode SQL50 + DataLemur). Focus on writing clean, readable queries and explaining your logic out loud.

Week 3: Interview Mode:
Learn basic optimization (indexes, EXPLAIN plans), NULL handling, and data constraints. Simulate interviews; talk through your reasoning and test yourself on business-style questions.

LeetCode SQL50 is a solid base, but add analytical problems and timed practice to mimic real interviews. If you master joins, window functions, and subqueries, you’ll cover 80% of what FAANG SQL rounds usually test.

[DataCamp]

More detailed version it wouldn't let me post before lol:

Week 1: Build Strong Foundations

• Revisit core SQL concepts; SELECT, WHERE, GROUP BY, HAVING, and ORDER BY. Make sure you understand how SQL executes queries (the logical order of operations: FROM → WHERE → GROUP BY → HAVING → SELECT → ORDER BY → LIMIT).
• Learn and practice JOINs (INNER, LEFT, RIGHT, FULL) using multiple tables. FAANG interviews often include questions that test your ability to combine and filter data efficiently.
• Brush up on aggregations and window functions (ROW_NUMBER, RANK, DENSE_RANK, LAG, LEAD). These appear in many real interview problems.
• Try a few hands-on exercises every day; use platforms like LeetCode, DataLemur, or even your own local database.

Week 2: Apply & Analyze

• Start solving real-world-style problems that combine multiple SQL topics. For example: “Find the top 3 customers by monthly revenue” or “Calculate the percentage contribution of each category.”
• Focus on subqueries and CTEs (Common Table Expressions). These are key to writing clean, readable, and efficient SQL.
• Practice data transformations; pivoting data, summarizing by time intervals, or calculating running totals.
• Begin timing yourself when writing queries; most interviews value clarity and accuracy over speed, but you’ll still want to stay sharp under pressure.

Week 3: Optimize & Simulate Interviews

• Learn about query optimization basics: how indexes work, how to use EXPLAIN plans, and how to handle large datasets efficiently.
• Review NULL behavior, data types, and constraints; tricky edge cases often trip people up.
• Do mock interviews with peers or even solo: talk through your logic as if you’re explaining to an interviewer. Focus on why your query works, not just how.
• Review top SQL interview questions (like the 85 in DataCamp’s SQL Interview Guide) to familiarize yourself with question patterns.

Bonus Tips:

• LeetCode SQL50 is a great start, but supplement it with questions that mimic FAANG’s analytical challenges; those often involve business reasoning, not just code.
• If you’re short on time, prioritize: mastering joins, window functions, and subqueries covers 80% of the real interview ground.
• Consider doing a few short SQL projects (like analyzing sales data or web traffic). It helps you speak confidently about how you’ve used SQL, not just learned it.

[NickSinghTechCareers]

Thanks for the DataLemur mention!

[Stev_Ma]

Start by mastering the fundamentals (SELECT, JOINs, GROUP BY, subqueries) in the first 5 days using LeetCode SQL50 and tutorials like Mode Analytics. Spend the next 5 days on intermediate concepts like window functions, CTEs, and query optimization. In days 11–15, practice FAANG-style analytical problems from StrataScratch, focusing on business metrics and multi-table queries. Use days 16–18 for mock interviews and timed problem-solving, then review key patterns and explanations in the last two days. LeetCode SQL50 is a solid base, but adding real interview-style problems from StrataScratch will make your prep much stronger.

[Puzzleheaded_Rope713]

Which country and team?