varenty02/databases-interview-questions

🟣 Databases Interview Questions Answered to help you get ready for your next Design Patterns & System Architecture interview.

Top 23 Databases interview questions and answers in 2021.

You can check all 23 Databases interview questions here 👉 https://devinterview.io/design/databases-interview-questions

🔹 1. What is Normalization?

Answer:

It is the process of eliminating redundant data and maintaining data dependencies.

Source: github.com/dhaval1406   

🔹 2. What are the advantages of NoSQL over traditional RDBMS?

Answer:

NoSQL is better than RDBMS because of the following reasons/properities of NoSQL:

• It supports semi-structured data and volatile data
• It does not have schema
• Read/Write throughput is very high
• Horizontal scalability can be achieved easily
• Will support Bigdata in volumes of Terra Bytes & Peta Bytes
• Provides good support for Analytic tools on top of Bigdata
• Can be hosted in cheaper hardware machines
• In-memory caching option is available to increase the performance of queries
• Faster development life cycles for developers

Still, RDBMS is better than NoSQL for the following reasons/properties of RDBMS:

• Transactions with ACID properties - Atomicity, Consistency, Isolation & Durability
• Adherence to Strong Schema of data being written/read
• Real time query management ( in case of data size < 10 Tera bytes )
• Execution of complex queries involving join & group by clauses

Source: stackoverflow.com   

🔹 3. Define ACID Properties

Answer:

• Atomicity: It ensures all-or-none rule for database modifications.
• Consistency: Data values are consistent across the database.
• Isolation: Two transactions are said to be independent of one another.
• Durability: Data is not lost even at the time of server failure.

Source: github.com/chetansomani   

🔹 4. What is Denormalization?

Answer:

It is the process of improving the performance of the database by adding redundant data.

Source: github.com/dhaval1406   

🔹 5. What are the difference between clustered and a non-clustered index?

Answer:

• A clustered index is a special type of index that reorders the way records in the table are physically stored. Therefore table can have only one clustered index. The leaf nodes of a clustered index contain the data pages.
• A non clustered index is a special type of index in which the logical order of the index does not match the physical stored order of the rows on disk. The leaf node of a non clustered index does not consist of the data pages. Instead, the leaf nodes contain index rows.

Source: github.com/dhaval1406   

🔹 6. How a database index can help performance?

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🔹 7. When should I use a NoSQL database instead of a relational database?

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🔹 8. What is Optimistic locking?

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🔹 9. What Is ACID Property Of A System?

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🔹 10. What is the cost of having a database index?

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🔹 11. How does B-trees index work?

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🔹 12. Explain the difference between exclusive lock and update lock

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🔹 13. What's the difference between a primary key and a unique key?

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🔹 14. What Is Sharding?

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🔹 15. What Is BASE Property Of A System?

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Thanks 🙌 for reading and good luck on your next tech interview!
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