50 Must-Know Databases Interview Questions and Answers 2024

Database Fundamentals

1.
What is a database management system (DBMS), and can you name some examples?
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2.
Explain the ACID properties in the context of databases.
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3.
What are the differences between SQL and NoSQL databases?
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4.
Describe a relational database schema.
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5.
What is a primary key, and why is it important?
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6.
Can you explain what a foreign key is and its role in the database?
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7.
What is database normalization, and why do we use it?
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8.
What is denormalization and when would you consider it?
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9.
Compare and contrast the DROP, DELETE, and TRUNCATE commands.
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10.
What is the difference between a full join and an inner join?
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SQL and Query Optimization

11.
How would you write an SQL query to fetch duplicate records from a table?
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12.
What is a prepared statement, and why would you use one?
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13.
What is the N+1 query problem and how can you solve it?
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14.
Explain the function of GROUP BY and HAVING clauses in SQL.
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15.
What are indexes and how do they work in databases?
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16.
What impact do JOIN operations have on database performance?
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17.
Define what a subquery is and provide a use case for it.
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18.
What is a correlated subquery?
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19.
Describe how you would optimize a slow SQL query.
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20.
Explain the EXPLAIN statement and how you use it in query optimization.
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Data Modeling and Design

21.
What is an Entity-Relationship (ER) model, and why is it useful?
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22.
Describe the process of converting an ER model into a relational database schema.
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23.
How do you design a scalable database schema for a high-traffic application?
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24.
What is database sharding, and what are its benefits and drawbacks?
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25.
Explain the term “data integrity” and how it’s enforced in databases.
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Transactions and Concurrency Control

26.
Can you explain the concept of transaction isolation levels?
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27.
What is a deadlock in databases, and how can it be resolved?
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28.
Describe optimistic vs. pessimistic locking.
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29.
How does a database ensure consistency during concurrent transactions?
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30.
What is a savepoint in a database transaction?
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Database Security

31.
What is SQL injection, and how do you prevent it?
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32.
Explain the role of access control in database security.
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33.
What are the best practices for storing passwords in a database?
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34.
How do you secure data transmission to and from a database?
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35.
Describe the use of encryption within databases for data at rest.
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Backup and Recovery

36.
What is a database snapshot, and when would you use one?
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37.
Explain the difference between logical and physical backups.
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38.
How would you restore a database from a backup file?
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39.
What are the common strategies for database disaster recovery?
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40.
How does point-in-time recovery work in databases?
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Performance Tuning and Scaling

41.
How would you handle a scenario where your database’s read load significantly increases?
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42.
What strategies exist for scaling writes in a high-volume database system?
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43.
Describe how connection pooling benefits database performance.
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44.
How do you monitor and identify database performance bottlenecks?
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45.
What is horizontal and vertical scaling in databases?
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NoSQL Databases

46.
Explain what a document store is and give an example of where it’s appropriate to use.
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47.
What is a graph database, and what are its typical use cases?
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48.
Describe the key-value store model and its typical applications.
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49.
How do you choose between consistency and availability in a NoSQL database, referencing the CAP theorem?
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50.
What is eventual consistency, and in what scenarios is it used?
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50 Databases interview questions

What is a database management system (DBMS), and can you name some examples?

Explain the ACID properties in the context of databases.

What are the differences between SQL and NoSQL databases?

Describe a relational database schema.

What is a primary key, and why is it important?

Can you explain what a foreign key is and its role in the database?

What is database normalization, and why do we use it?

What is denormalization and when would you consider it?

Compare and contrast the DROP, DELETE, and TRUNCATE commands.

What is the difference between a full join and an inner join?

How would you write an SQL query to fetch duplicate records from a table?

What is a prepared statement, and why would you use one?

What is the N+1 query problem and how can you solve it?

Explain the function of GROUP BY and HAVING clauses in SQL.

What are indexes and how do they work in databases?

What impact do JOIN operations have on database performance?

Define what a subquery is and provide a use case for it.

What is a correlated subquery?

Describe how you would optimize a slow SQL query.

Explain the EXPLAIN statement and how you use it in query optimization.

What is an Entity-Relationship (ER) model, and why is it useful?

Describe the process of converting an ER model into a relational database schema.

How do you design a scalable database schema for a high-traffic application?

What is database sharding, and what are its benefits and drawbacks?

Explain the term “data integrity” and how it’s enforced in databases.

Can you explain the concept of transaction isolation levels?

What is a deadlock in databases, and how can it be resolved?

Describe optimistic vs. pessimistic locking.

How does a database ensure consistency during concurrent transactions?

What is a savepoint in a database transaction?

What is SQL injection, and how do you prevent it?

Explain the role of access control in database security.

What are the best practices for storing passwords in a database?

How do you secure data transmission to and from a database?

Describe the use of encryption within databases for data at rest.

What is a database snapshot, and when would you use one?

Explain the difference between logical and physical backups.

How would you restore a database from a backup file?

What are the common strategies for database disaster recovery?

How does point-in-time recovery work in databases?

How would you handle a scenario where your database’s read load significantly increases?

What strategies exist for scaling writes in a high-volume database system?

Describe how connection pooling benefits database performance.

How do you monitor and identify database performance bottlenecks?

What is horizontal and vertical scaling in databases?

Explain what a document store is and give an example of where it’s appropriate to use.

What is a graph database, and what are its typical use cases?

Describe the key-value store model and its typical applications.

How do you choose between consistency and availability in a NoSQL database, referencing the CAP theorem?

What is eventual consistency, and in what scenarios is it used?

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