Top 50+ Popular Database Interview Questions and Answers

Gone are the days of traditional file-based systems. With the advent of new technologies, particularly, in the database and database-related avenues, the demand for professionals adept with domain-specific knowledge has increased. Now, Management Information Systems or their variants are used widely to store and manage data efficiently and time-saving process. This, in turn, has made database skills a much-needed requisite in scores of jobs. However, preparing for a personal interview can be unsettling for the best of us. The interviewer might ask you questions aimed at evaluating your knowledge and skills, assessing your creativity, and your command of the subject. So, in this blog, we have curated some popular Database interview questions that can help you in preparing for your upcoming interview!

10 Most Popular Database Interview Questions

Before we delve into a list of interview questions, let us go through the most popular Database interview questions and their answers. 

1. What is Cardinality?
   It is a concept borrowed from Mathematics. In the database world, Cardinality is a concept that is related to the counts in a relationship, one-to-one, one-to-many, and many more. In Structured Query Language, cardinality means the uniqueness of data values in a specific column of the database table. If the cardinality is low, there will be more duplicate elements in a column.

2. What are the advantages of DBMS over a traditional file-based system?
   A typical file-based system has certain limitations that are overcome by DBMS. These difficulties that arose in the traditional system giving an edge to DBMS are:

• Difficulty in accessing data
• Integrity problems
• Data inconsistency and redundancy
• Security problems
• Concurrent access by multiple users

3. What is database normalization?
   The process of analyzing the relation schemas based on their functional dependencies and primary keys to achieving desirable properties in what is database normalization. Desirable properties result in

• Minimizing delete, insertion, and update anomalies
• Reducing redundancy in the data.

4. What are super, primary, and foreign keys?

• A set of attributes of a relation schema on which all attributes of the schema are functionally dependent are called super keys.
• A type of candidate key that is selected and becomes most important becomes the primary key. A table can have only one primary key.
• A field or collection of fields in one table that can identify a row of another table is called a foreign key. 

5. What is the difference between HAVING and WHERE clauses?
   HAVING clause is used to specify a condition for a group or an aggregate function. It segregates rows after grouping. Unlike this, the WHERE clause selects before grouping. It cannot contain aggregate functions. The WHERE clause is broadly used while selecting rows based on conditions, on the other hand, the HAVING clause is used in column operations and only applied to aggregated rows or groups.

6. What is a database transaction?
   A database transaction is a set of functions or database operations that are to be treated as a whole i.e. either all the operations are executed or none of them are. 

7. What are the uses of view?

• The view can be used to conjoin and thereby simplify multiple tables into one simple table.
• It can be used to aggregate data and perform aggregate functions to get the results as a part of the table
• It can reduce the complexity of a table
• The view takes less space to be stored
• It can represent the subset of the data contained in a table. This reduces the exposure of the table and at the same time increases security. 

8. Define DBMS

DBMS stands for Database Management System. It is basically a collection of application programs. It allows users to operate different functions such as organization, restoration, and gain information about data.

9. Define RDBMS

It is Relational Database Management System and is based on a relational model of data. It is stored in databases in different and separate tables but related to the same column. It is easily accessible with SQL.

10. What do you understand by Data Redundancy?

When data is duplicated or copied it is known as data redundancy. It is present in multiple locations, taking up space. Data redundancy is a waste of storage space.

List of Other 25 Popular Database Interview Questions

To help you further with your interview, we have enlisted some important and popular Database interview questions that are commonly asked. Scan through them to get an idea:

1. What is SQL?
2. When might someone denormalize their data?
3. Describe the differences in the first through fifth normalization forms.
4. What are the elements of ERD?
5. What is Join?
6. How to print duplicate rows in a table?
7. What is Identity?
8. What is a Trigger?
9. What is a stored procedure?
10. State the major points of differences between a Trigger and a Stored Procedure.
11. What are database indexes?
12. What are clustered and nonclustered indexes?
13. Explain the terms DDL, DML, and DCL in SQL. State the major differences between them. 
14. Differentiate between an Inner and Outer join. 
15. How would you define an Entity? Is Entity Type and Entity Set the same?
16. Define Index Hunting and also state the major points of difference between the Cluster and Non-cluster index. 
17. Are 2NF and 3NF the same?
18. What do you understand by the term “Sub-query”? Explain the types and properties. 
19. Briefly describe the Tier-2 and Tier-3 architecture. 
20. What is truncation? Explain its properties. 
21. What is partitioning? She light on its importance and use. 
22. Define RDBMS and explain how it is different from DBMS. 
23. Elucidate the terms “Self-Join” and “Cross-Join”. 
24. Explain Normalization and De-Normalization.
25. What is BCNF?

Top 10 Database Interview Questions for Experienced

1. What are tables and Fields?
2. What is a primary key?
3. What is a unique key?
4. What are the types of join and explain each?
5. What is Denormalization and Normalization?
6.  What are all the different types of indexes?
7. What is a relationship and what are they?
8. What is a cursor?
9. What is a query?
10. What is a subquery?
11. What is a trigger?
12. What are local and global variables and their differences?
13. What is a constraint?
14. What is the difference between Cluster and Non-Cluster Index?
15. What are all types of user-defined functions?

Top 10 Database Interview Questions for Fresher

1. What is DBMS used for?
2. What is meant by a Database?
3. What are the advantages and importance of DBMS?
4. What is the purpose of normalization in DBMS?
5. What are the different types of languages that are available in the DBMS?
6. What is the purpose of SQL?
7.  What are the main differences between the Primary key and Unique Key?
8. What is the main difference between UNION and UNION ALL?
9. What are ACID Properties?
10. What is Correlated Subquery in DBMS?

How to Ace the Interview?

As with any other job, the interviewer is likely to ask questions that will test your technical as well as theoretical skills mentioned in your resume.

• You should have a complete idea about the various technologies listed in your resume.
• While it is beneficial to be updated about the latest trends in the field, having a strong command over the basics is absolutely necessary.
• Be ready to showcase your technical skills.
• The questions are likely to be technical and would require highly detailed answers for the interviewer to understand your potential. Don’t hold back from answering the question with an in-depth answer.
• Last but not least, practice the important and most popular Database interview questions given above!

Top 100 SQL Query Interview Questions

We hope this blog gave you an idea about the popular Database interview questions that might be asked in your interview. Exploring Database Management or related courses abroad? Not sure how to go about it? Then take the assistance of experts at Leverage Edu who will provide guidance right from choosing a program to completing the admission formalities of a university abroad!