SQL Interview Questions

This document provides a curated list of SQL interview questions commonly asked in technical interviews. It covers topics ranging from basic SQL syntax and data types to advanced concepts like joins, subqueries, window functions, and database design. The list is updated frequently to serve as a comprehensive reference for interview preparation.

Questions asked in Google interviews

1. Explain window functions and their applications in analytical queries.
2. Write a query to find users who have logged in on consecutive days.
3. How would you optimize a slow-performing query that involves multiple joins?
4. Explain the difference between RANK(), DENSE_RANK(), and ROW_NUMBER().
5. Write a query to calculate a running total or moving average.
6. How would you handle hierarchical data in SQL?
7. Explain Common Table Expressions (CTEs) and their benefits.
8. What are the performance implications of using subqueries vs. joins?
9. How would you design a database schema for a specific application?
10. Explain how indexes work and when they should be used.

Questions asked in Amazon interviews

1. Write a query to find the nth highest salary in a table.
2. How would you identify and remove duplicate records?
3. Explain the difference between UNION and UNION ALL.
4. Write a query to pivot data from rows to columns.
5. How would you handle time-series data in SQL?
6. Explain the concept of database sharding.
7. Write a query to find users who purchased products in consecutive months.
8. How would you implement a recommendation system using SQL?
9. Explain how you would optimize a query for large datasets.
10. Write a query to calculate year-over-year growth.

Questions asked in Microsoft interviews

1. Explain database normalization and denormalization.
2. How would you implement error handling in SQL?
3. Write a query to find departments with above-average salaries.
4. Explain the different types of joins and their use cases.
5. How would you handle slowly changing dimensions?
6. Write a query to implement a pagination system.
7. Explain transaction isolation levels.
8. How would you design a database for high availability?
9. Write a query to find the most frequent values in a column.
10. Explain the differences between clustered and non-clustered indexes.

Questions asked in Meta interviews

1. Write a query to analyze user engagement metrics.
2. How would you implement a friend recommendation algorithm?
3. Explain how you would handle large-scale data processing.
4. Write a query to identify trending content.
5. How would you design a database schema for a social media platform?
6. Explain the concept of data partitioning.
7. Write a query to calculate the conversion rate between different user actions.
8. How would you implement A/B testing analysis using SQL?
9. Explain how you would handle real-time analytics.
10. Write a query to identify anomalies in user behavior.

Questions asked in Netflix interviews

1. Write a query to analyze streaming patterns and user retention.
2. How would you implement a content recommendation system?
3. Explain how you would handle data for personalized user experiences.
4. Write a query to identify viewing trends across different demographics.
5. How would you design a database for content metadata?
6. Explain how you would optimize queries for real-time recommendations.
7. Write a query to calculate user engagement metrics.
8. How would you implement A/B testing for UI changes?
9. Explain how you would handle data for regional content preferences.
10. Write a query to identify factors affecting user churn.

Questions asked in Apple interviews

1. Explain database security best practices.
2. How would you design a database for an e-commerce platform?
3. Write a query to analyze product performance.
4. Explain how you would handle data migration.
5. How would you implement data validation in SQL?
6. Write a query to track user interactions with products.
7. Explain how you would optimize database performance.
8. How would you implement data archiving strategies?
9. Write a query to analyze customer feedback data.
10. Explain how you would handle internationalization in databases.

Questions asked in LinkedIn interviews

1. Write a query to implement a connection recommendation system.
2. How would you design a database schema for professional profiles?
3. Explain how you would handle data for skill endorsements.
4. Write a query to analyze user networking patterns.
5. How would you implement job recommendation algorithms?
6. Explain how you would handle data for company pages.
7. Write a query to identify trending job skills.
8. How would you implement search functionality for profiles?
9. Explain how you would handle data privacy requirements.
10. Write a query to analyze user engagement with content.