SQL Interview Questions for Data Science

Welcome to my SQL interview preparation repository! Below are a collection of common SQL questions and theoretical concepts that are frequently asked in Data Science interviews.

Common Questions

1. Write a query to add multiple columns in a table.
2. Write a query to add/delete multiple columns in a table.
3. Write a query to find out the 2nd highest value in a table.
4. Find the maximum value without using ORDER BY.
5. Find managers of all employees.
6. Use of wildcards.
7. If-else based questions.
8. Find category-wise top value.
9. Find/delete all the duplicate values.
10. Joining tables.

Theory Questions

1. SQL Vs NoSQL Databases.
2. Tables required for many-to-many relationships.
3. Draw schema design for swiggy.
4. Types of Joins -> Union Vs Union All
5. OLAP Vs OLTP [Normalized Vs Denormalized Data]
6. Database keys
7. Types of normalization
8. What are indexes in Databases and what are its types
9. What are transactions in databases? Explain ACID properties.
10. Define
    • Views
    • Stored Procedures

Feel free to contribute by adding more questions or improving existing solutions!

Contributing

Contributions are welcome! If you have additional SQL questions or improvements to existing solutions, feel free to open a pull request.

License

This repository is licensed under the MIT License. See the LICENSE file for details.