20 Most Commonly Asked MySQL Interview Questions

In today’s world where data becomes increasingly crucial for businesses and organizations, the ability to manage and analyze data efficiently is more important than ever.

More specifically, MySQL is a popular database management system that allows its users to store and fetch data quickly and securely. So, whether you are just starting out in data management or preparing for an interview, having a solid understanding of MySQL is crucial.

In this post, we will dive into some common interview questions related to MySQL basics, database design, SQL queries, performance optimization, and security.

Basic MySQL Questions

Let’s start the blog with an introduction to key concepts related to databases and MySQL.

1. Define Database and How Is It Used in MySQL?

A database is defined as the data collection organized in a structured manner. In MySQL, data is stored and managed in a database. It comprises single or multiple tables, each of which contains the required data. Moreover, MySQL permits you to add, update, or remove records or data from a specific table.

2. What Is SQL and How Is It Used in MySQL?

SQL is an abbreviation for Structured Query Language and it is used for communicating with relational databases, such as MySQL. More specifically, SQL can be utilized to create, update, or fetch data from the MySQL database. You can also use it to perform complex operations on extensive data.

3. What Is MySQL?

MySQL is a freely available open-source Database Management System (DBMS) that is primarily used for web apps and other software. Back in 2010, it was acquired by Oracle Corporation.

MySQL has an active and strong community that contributes to its development. It is different from other DBMSs because of being free to use. This makes MySQL an ideal choice for developers and organizations looking for an effective management system.

4. What Are the Benefits of Using MySQL?

Here are some of the primary advantages or benefits of MySQL usage:

  • MySQL is simple to use and supported by a large community.
  • It is a reliable and scalable database management system.
  • Based on its flexibility and versatility, it is an ideal choice for businesses.
  • It supports several services and tools that can assist developers in developing web apps and other software.

MySQL Database Design Questions

This section focuses on the design principles of a database, such as normalization, denormalization, relationships between tables, and the advantages/disadvantages of using a relational database like MySQL.

1. Explain Database Normalization and Its Important in MySQL

The process of organizing or managing data in a database for improving data integrity and reducing data redundancy is known as Database Normalization. In MySQL, this operation can be performed by breaking down a large table into smaller easier to manage tables, where each of them has a specific purpose.

This helps to avoid data-related errors and inconsistencies and makes it easy to modify, update, or delete the data.

2. What is Denormalization in MySQL?

Denormalization is the technique of adding duplicated data to a database to improve its efficiency. In MySQL, it is utilized for adding redundant data to single or multiple data for eliminating the requirements for joining for other complicated queries.

Moreover, Denormalization is mainly used in scenarios where performance is more essential as compared to data consistency, such as in analytics applications or data warehousing.

3. Describe Relationship Types Between Tables in MySQL?

In a MySQL database, there are three different kinds of relationships that are explained below:

  • one-to-one – It is the type of relationship where one record is connected to a single record in another table.
  • one-to-many – When multiple records in one table are connected to one record in another table, this is known as a one-to-many relationship.
  • many-to-many – many-to-many refers to the type of relationship where multiple records of one table are connected to many records in another table.

4. What Are MySQL Advantages and Disadvantages?

Using a relational database like MySQL has many advantages, such as:

  • It can enforce data integrity and consistency.
  • It offers support for executing complex transactions and queries.
  • It is flexible and scalable.
  • Additionally, the provided tools and services facilitate the use of relational databases, which are also very popular.

However, there also exist some significant disadvantages as well like:

  • MySQL is complex which makes it difficult to maintain and manage.
  • While performing certain types of operations and queries, it can be less efficient as compared to other databases.
  • Lack of support for some specific data types, such as semi-structured or unstructured data.

SQL Queries Questions

Check out the given important questions related to SQL queries and topics like SELECT statement, JOIN, subquery, and UNION.

1. Explain SELECT Statement in MySQL?

In a MySQL database, the SELECT statement retrieves or fetches data from single or multiple tables. It permits you to define the number of columns you want to retrieve and specifies the relevant sorting or filtering criteria.

Check out the provided syntax for using the SELECT statement.

SELECT col1, col2 FROM table1;

According to the given query, the SELECT statement will fetch the records from col1 and col2 from the given table1.

Note: Refer to our other dedicated article to know more about manipulating data in MySQL.

2. What Are the Different Types of JOINs in MySQL?

A JOIN is utilized for aggregating or combining data from two or more tables.

In MySQL, there are four different JOIN types:

  • INNER JOIN – This type of JOIN simply outputs only the rows that get matched in both tables.
  • LEFT JOIN – It returns all rows from the left table together with any matching rows from the right table.
  • RIGHT JOIN – It returns all rows from the right table together with any matching rows from the left table.
  • FULL OUTER JOIN – It is utilized for getting all rows or records from both tables.

3. What Is the Purpose of Using a Subquery in MySQL?

A query that is nested inside another query is called a subquery. It permits you to fetch data based on the outcomes of another query.

For instance, in the below-given query, the subquery will fetch the list of customers who ordered something within February 2023.

SELECT * FROM customers WHERE customer_id IS IN (ORDER_DATE > '2023-02-01' AND customer_name IS SELECTED FROM orders);

As a result, the subquery will display the names of all of the customers whose ORDER_DATE is greater than February 1, 2023.

4. Discuss the Use of UNION in MySQL

In MySQL, the output of two or more SELECT statements is combined using a UNION. It can be utilized when it is required to fetch data from many tables or views having similar structures.

For instance, you could use a UNION to retrieve all of a customer’s orders, whether they were placed in person or online.

SELECT order_id, order_date, 'online' as source FROM online_orders WHERE customer_id = 789
SELECT order_id, order_date, 'in-person' as source FROM in_person_orders WHERE customer_id = 789;

Here, UNION combines the result of two SELECT statements, one for online orders and one for in-person orders, and adds a new column to check the source of each order. Regardless of where the orders were placed, the subsequent query would return all of customer 789’s orders.

MySQL Performance Optimization Questions

This section compiled the questions related to optimizing MySQL database performance, including the use of indexes, stored procedures, caching mechanisms, and other performance-enhancing techniques.

1. What Are Indexes and How Do They Improve MySQL Query Performance?

In MySQL, Indexes are database objects that help with data retrieval speed. They work by developing a separating data structure that enables the database to quickly retrieve the rows that correspond to a specific query.

Moreover, for large databases, the performance of queries can be significantly improved by using these objects.

2. What Is a Stored Procedure?

An executable SQL script that has been precompiled and is stored on the database server is called a Stored Procedure. By reducing network traffic and enhancing security, stored procedures can assist MySQL in functioning properly.

They are primarily utilized for complex queries that are frequently executed.

3. Explain the Types of Caching Mechanisms in MySQL?

In MySQL, there are many caching mechanisms, such as key cache, query cache, and table cache. While the key cache holds index blocks to facilitate index lookups, the query cache keeps the results of frequently conducted queries in memory.

To speed up table operations, the table cache saves table information in memory.

4. How to Optimize MySQL for High-traffic Websites?

For optimizing a MySQL database for high-traffic applications or websites, you can use the following approaches:

  • Reducing network traffic and increasing security by utilizing stored procedures.
  • Using caching techniques to increase the speed of data retrieval.
  • Minimizing connection overhead by using connection pooling.
  • Normalizing the tables in the database and eliminating any duplicated or redundant records.
  • Using a load balancer to allocate traffic between several servers.

MySQL Security Questions

This last section addresses security concerns related to MySQL, such as preventing SQL injections, best practices for securing the MySQL database and ensuring data integrity.

1. What are SQL Injections?

Attackers can steal, alter, or destroy data by injecting malicious SQL code into a database query known as SQL Injections. However, you can utilize escape input data, parameterized statements, or queries to stop SQL injections in MySQL.

2. How to Secure a MySQL Database?

Follow the given practices for securing a MySQL database:

  • Create strong, unique passwords for each account.
  • Validate the database access.
  • Update and patch the MySQL server software regularly.
  • Define encryption to secure sensitive data.
  • Periodically audit or check database activity and access.
  • Disable unused services and functionalities.
  • Back up the database frequently, and test the restoring data operation.

3. How to Ensure Data Integrity in MySQL?

You can consider the listed methods to ensure data integrity in a MySQL database:

  • Define constraints, such as foreign keys and unique indexes, to impose data integrity rules.
  • Use transactions to make sure a collection of connected database changes is atomic and consistent.
  • Utilize triggers to automate specific validations or actions whenever any data manipulation information is performed.
  • Validate and clean data frequently to get rid of redundant entries.
  • To avoid errors or corruption, the database should be regularly monitored and maintained.

To be interested in pursuing a career in data management, you must have a solid understanding of MySQL. Moreover, It is essential to have a clear understanding of MySQL fundamentals like databases to more complex ideas like design, SQL queries, and performance optimization.

By mastering the given MySQL interview questions, you will be well-equipped for your dream job and can make a valuable contribution to any organization or business that relies on data-driven decision-making.

Did we miss any important MySQL interview questions in this article? do share them in the comments below.

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Ravi Saive
I am an experienced GNU/Linux expert and a full-stack software developer with over a decade in the field of Linux and Open Source technologies

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22 thoughts on “20 Most Commonly Asked MySQL Interview Questions”

  1. Well he tried hos best. The good thing, he web site, blog was on my top Google search. So he did something right.

    Let say thank you for taking the time and explaining something obvious unless u are new to MySQL.


  2. Sir,
    I want to become a DB tester. I have to test an application which is CRM (Salesforce) based. Could you please guide me to write DB testing scenarios for application.

    Thanks a lot

  3. Seems that “How will you show all the records from table ‘xrt’ where name is not ‘tecmint’ and web_address is ‘tecmint.com’?” actually returns a record where name=’tecmint’….

    Very helpful site :)


    The ‘helpful’ remark isn’t ment ironically ;)

  4. Have to agree with all the others, this article is flawed You would not be asked to show such basic knowledge at an interview for a DBA postition.

    I notice that the author replied to the first comment that praised his work, but does not have the gumption to reply to comments that are critical of his work.

  5. What a bunch of crap questions – a DBA should know SQL and the inner details of the DB the company users eg. MySQL in the above examples.
    All of the questions abover are for home use and nothing else.

    As Barak mentions then a DBA works with SQL, inner optimizations of the DB (storages engines/partitioning tables, master-master/master-slave etc.) setup.

    A DBA’s primary job is to make sure the DB is running optimally and help/assist developers in optimizing poorly written SQL queries and optimize indexes and implement backup that does not affect the systems performance and restore options etc.

    Poorly written questions for getting page hits. Please don’t use novice questions for job interview question examples. Please change the title to “How do I get to know my own personal MySQL server” or something like that.

    • I would change the title to “Please tell me how great I am because I wrote a bunch of stupid questions that any novice could learn in less than 5 minutes.”

      That’s all the author is doing.

  6. I’m afraid those are all novice/entry-level questions one would ask a junior web programmer, none of the question answers indicate any real DBA skills, about 80% of the questions concern generic user-level SQL syntax and answering them test’s the interviewee’s memory rather then his deep understanding of MySQL.
    If I was hiring a MySQL DBA, I would have to ask questions about the following issues:
    1. What are storage engines and what are the main differences between MyISAM and Innodb, Advanced DBAs would have to be able to name at lease one more storage engine and specify what could it be used for.
    2. Disk space management (DBA candidate would absolutely have to know about innodb_files_per_table)
    3. Memory management
    4. SQL Execution Plan analysis and and tuning (I would expect developers to know this too)
    5. How to tell what MySQL is doing right now and when stuff is going slow
    6. How to do backups and restores
    7. How MySQL replication works and how to set it up
    8. Data security – How do I prevent access to specific data, how to store sensitive information such as passwords and how to prevent SQL injection.

    • Exactly. These “questions for interviews” articles are nothing but click bait so he can get attaboys from his friends. The author doesn’t care one whit about producing quality articles or responding to people who politely point out that his articles contain factual errors.

      I had hoped that politely pointing out the errors would result in improvements in the quality of the articles here, because I admire people who take the time to explain things to newcomers, but instead it resulted in the author complaining about people being critical of him. Apparently, if you don’t care to feed his ego and point out that his articles need correcting, you are being too negative.

      Based on the content of his articles alone, I wouldn’t hire this guy even as an entry level admin. He obviously thinks he knows way more than he actually does.


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