Top MySQL Interview Questions and Answers

Introduction

Level Up Your MySQL Skills and Land Your Dream Job

Looking to advance your IT career in the database field? Having strong MySQL expertise is a major asset, as it's a highly sought-after skill for critical business applications.

This guide provides a targeted set of MySQL interview questions specifically designed for IT professionals with 5+ years of experience. By mastering these questions, you'll gain a deeper understanding of key concepts and showcase your problem-solving abilities during your next interview.

What You'll Find:

• In-depth MySQL interview questions for experienced professionals
• Coverage of essential topics for advanced database management
• Preparation for real-world scenarios you might encounter on the job

Don't wait! Start preparing today and unlock new opportunities in the database domain.

MySQL Interview Questions And Answers For Freshers

Q1). How to compare MySQL and SQL?

• SQL means Structured Query Language that is used to interact with databases like MySQL. It is a database that is used to store various types of data and keeps it safe.
• SQL is a computer language, and MySQL is a software application or program.
• SQL is used for maintaining database management systems whereas MySQL is used for storing, data handling, deleting, or modifying data.

Q2). What is MySQL?

MySQL is a multi-threaded or multi-user database management system having more than 11 million installations. It is the world’s second largest most popular and widely used open source database. Using MySQL is free of cost for developers, but enterprises have to buy the licensed version. It is supported by Oracle and based on Structured Query Language. It supports a wide range of operating systems like Windows, Linux, and Unix, etc. 

Q3). In which language MySQL is written?

MySQL is written in C, and C++ language, and its SQL parser is written in YACC language.

Q4). What are the technical specifications of MySQL?

MySQL is a client-server based application that includes:

• A multithreaded SQL Server supports various client programs and libraries
• It includes different backends
• It includes a wide range of programming interfaces and administrative tools

Q5). Why is MySQL so popular?

MySQL is a database server that is fast, reliable, and easy to use. It can be downloaded from the internet from a single click.

Q6). What are the different SQL data types?

The different SQL data types include numeric, character, date/time, Unicode, miscellaneous, and binary. These data types determine the type of data that can be stored in a database table.

Q7). What do you understand about Heap Tables?

These are available in memory for high-speed storage temporarily. It does not allow BLOB or text fields; only comparison operators are allowed. Heap tables and indexes do not support an auto-increment function and should be NOT NULL.

Q8). Name the default port for the MySQL Server

It is 3306.

Q9). How is MySQL better than Oracle?

These are the reasons what makes MySQL better than Oracle:

• It is an open source database system suitable for almost all organizations without any major costs involved in it
• It is portable with a GUI interface and a command prompt
• MySQL administration is supported by the MySQL query browser

Q10). How to compare FLOAT and DOUBLE keywords in MySQL?

• To store float numbers, FLOAT keyword is used with four byes and eight bits accuracy
• To store float numbers, the DOUBLE keyword is used with eight bytes and 18 bits accuracy

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Q11). How can you represent ENUMs and SETs internally?

They are used to represent the power of two because of storage optimizations.

Q12). How to compare Char-length and length keywords in MySQL?

Char-length is related to character count, whereas length keyword is related to the byte count.

Q13). What is the purpose of using ENUM in MySQL? 

ENUM is a string object in MySQL that allows you to define a predefined set of values. It is commonly used during table creation to specify a column that can only contain one of the specified values from the predefined set. Using ENUM helps enforce data integrity and restricts the allowed values for a particular column.  

Q14). What is REGEX in MySQL? 

REGEX, short for regular expression, is a pattern-matching feature in MySQL. It allows you to search for specific patterns within text or string values. By defining a regular expression pattern, you can perform advanced searching and matching operations, making it a powerful tool for data retrieval and manipulation in MySQL.  

Q15). How do CHAR and VARCHAR differ in MySQL? 

CHAR and VARCHAR are both string data types in MySQL, but they differ in terms of storage and retrieval behavior. The CHAR data type has a fixed length, meaning it always occupies the same amount of storage space regardless of the length of the stored value. In contrast, VARCHAR is a variable-length data type, where the storage space used varies based on the actual length of the value stored. In MySQL, a CHAR column length is specified and fixed, while a VARCHAR column length can range from 1 to 255 characters.

Q16). What is the possible number of string types available for a column?

• SET
• BLOB
• ENUM
• CHAR
• TEXT
• VARCHAR

A better understanding of the functioning of SQL Operators can help you with these sorts of interview questions.

Q17). How to get the current MySQL version?

Here is the command to get the current MySQL version:

SELECT VERSION ();

Q18). Name a few drivers in MySQL

Here is the list of drivers available in the MySQL:

• PHP Driver
• JDBC/ODBC Driver
• C WRAPPER
• PYTHON Driver
• PERL Driver
• RUBY Driver
• CAP11PHP Driver

Q19). What are storage engines and how data is stored in storage engines?

Storage engines are table types, and data is stored in the storage engine using various techniques given below:

• Indexing
• Locking levels
• Storage mechanism
• Functions and capabilities

MySQL Interview Questions And Answers For Intermediates

Q20). How to compare a primary key and a candidate key?

Each row in a table is identified uniquely by the primary key. There is only a primary key within a table. A primary key can be used as the candidate key and vice versa based on requirements.

A sound understanding about what is candidate key SQL? and how to implement them in different tables.

Q21). How to login to a MySQL account when using a UNIX shell?

Here is the command for logging to a MySQL account when using a UNIX shell:

#[mysql dir]/bin/mysql – hostname –u -p

Q22). What is the purpose of MyISAM in MySQL?

It is used to compress the myISAM tables that reduce the memory or disk usage.

Q23). What is the maximum size of a Heap Table?

There is no limit on the maximum size of a heap table, but it should be controlled by MySQL config variable named as:

Max_heap_table_size

Q24). How to differentiate the myISAM static and myISAM dynamic?

For myISAM static, all the fields have fixed length while myISAM dynamic can accommodate variables of different lengths.

Q25). What will happen when a column is set to auto increment and reaches its maximum value?

It will stop incrementing and produce errors for further inserts.

Q26). What will happen when a column within a table is defined as TIMESTAMP?

It gets the current timestamp whenever rows are altered.

Read our blog to understand all about SQL Joins and Subqueries in a table.

Q27). What do you understand about federated tables?

They allow access to tables located on other databases of the server.

MySQL Interview Questions and Answers for Advanced

Q28). How can you see all the indexes for a table?

To see all the indexes for a table, you can use the following command:

SHOW INDEX FROM ;

Q29). How to find which auto increment operation was applied to the Last Insert?

LAST  INSERT_ID

This operator returns the last value assigned by the auto-increment operator and there is no need to specify the table name.

If you want to grow your career as an SQL Developer, you must have a sound understanding of how to become an SQL developer and the associated details.

Q30). How to get the total number of rows affected by a query?

The total number of rows affected by a query can be given as:

SELECT COUNT (user_id) FROM users;

Q31). Is MySQL case-sensitive or not?

No, it is not case-sensitive. All commands given below have the same meaning.

• SELECT VERSION()
• CURRENT_DATE 
• select version() 
• current_date 
• seleCT vErSiOn() 
• Current_DATE

Q32). What are the comparison operators that can be used for a column in MySQL?

MySQL provides several comparison operators that can be used with columns in SELECT statements. Some commonly used comparison operators include:  

• Equal To (=): This operator checks if a column value is equal to a specific value.
•  Not Equal To (<> or !=): This operator verifies if a column value is not equal to a specific value. 
• Greater Than (>), Less Than (<): These operators compare if a column value is greater than or less than a given value, respectively. 
• Greater Than or Equal To (>=), Less Than or Equal To (<=): These operators check if a column value is greater than or equal to, or less than or equal to, a specified value. 
• LIKE: The LIKE operator is used to perform pattern matching with wildcard characters (% and _). It helps search for values that match a specified pattern. 
• AND, OR: These logical operators are used to combine multiple conditions in a query. The AND operator requires all conditions to be true, while the OR operator only requires one of the conditions to be true.

Q33). How to convert between UNIX and MySQL stamps?

The following command can be used to convert from MySQL timestamp to UNIX timestamp.

UNIX_TIMESTAMP

The following command can be used to convert from UNIX timestamp to MySQL timestamp:

FROM_UNIXTIME

Q34). What is the significance of “%” and “_” operators in the LIKE statement?

“%” corresponds to zero or more characters and “_” operator exactly represents only one character.

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Q35). How to compare “LIKE” and “REGEXP” operators in MySQL?

These two operators are used to express with % and ^: 

SELECT * FROM employee WHERE em_name REGEXP "^b"; SELECT * FROM employee WHERE em_name LIKE "%b";

Q36). Write a few significant differences between TEXT and BLOB.

A BLOB is a large binary object that has the capability of holding a voluminous amount of data. There are a total of four types of BLOB in MySQL.

• TINYBLOB
• BLOB
• MEDIUMBLOB
• LONGBLO

BLOB and TEXT are different in terms of maximum length of values they can hold. TEXT is a BLOB that is case-sensitive in nature and divided into four categories. These are:

• TINYTEXT
• TEXT
• MEDIUMTEXT
• LONGTEXT

TEXT is usually case-sensitive, and BLOBs are not case-sensitive for TEXT values.

Q37). How to compare mysql_fetch_array and mysql_fetch_object?

Here are the notable differences among mysql_fetch_array and mysql_fetch_object:

• mysql_fetch_array returns a result row as a regular array or associative array from the database
• mysql_fetch_object returns a result row as an object from the database

Q38). How to run batch mode in MySQL?

Here is the command to run match mode in MySQL: 

mysql ; mysql mysql.out

Q39). How to store myISAM in different formats?

Each myISAM table is stored in three formats:

• The'.frm' file stores the table definition
• the data file has a '.MYD' (MYData) Extension
• The index file has a '.MYI'(MYIndex) extension

Q40). What are the different types of tables available in MySQL?

“MYISAM” is the default storage engine in MySQL. Here is the list of different types of tables available in MySQL:

MYISAM, Heap, Merge, INNO DB, ISAM.

Q41). What do you understand about the term ISAM in MySQL?

ISAM means Indexed Sequential Access Method. It is used to store and retrieve data on secondary devices like tapes. Ace your upcoming SSAS interview with confidence, by reading our Top 75 Interview Questions for SAAS.

Q42). Do you know about InnoDB in MySQL?

It is a transaction-safe storage engine proposed by the Innobase which is an Oracle Corporation now.

Here’s an image of the InnoDB storage engine in MySQL

Q43). How to optimize the DISTINCT operator in MySQL?

DISTINCT is first converted to a GROUP BY clause and then combined with an ORDER BY clause.

Q44). How many columns can be used to create indexes?

A total of 16 indexed columns can be used to create indexes.

Q45). What is the command to display the top 50 rows in MySQL?

Here is the command for displaying top 50 rows in MySQL:

SELECT * FROM LIMIT 0,50;

It is not easy learning these commands theoretically but you should practice them practically to be prepared for such SQL join interview questions. For this purpose, join an online training program or check the demo class first to make sure that you have chosen the right institute.

Q46). How to enter characters as HEX numbers?

To enter characters as HEX numbers, you should enter HEX numbers with single quotes and prefix (x).

Q47). What is an Access Control List in MySQL?

An Access Control List (ACL) is a set of permission associated with an object. It is the basis of the server’s security model and helps in troubleshooting problems like users are not able to connect, not able to access data, etc. MYSQL stores the ACL in the cache memory. Every time a user tries to run or authenticate a command, MySQL checks the permissions or authentication information against the Access Control List (ACL) in a specific order.

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Q48). How will you define joins in MySQL?

MySQL uses joins to query data from two or more tables. There are a total of four types of joins in MySQL. These are Inner join, Full join, Right join, and left join. Inner join returns rows even if there is one single match in both the tables. Focus on practicing to be prepared for such SQL join interview questions. 

LEFT join returns all rows from the LEFT table even if there are no matches for the RIGHT table. RIGHT join returns all rows from the RIGHT table even if there are no matches for the LEFT table. Full join returns rows where there is at least one match in both the tables.

You might want to take this online SQL training to learn more about this. 

Q49). What do you understand about DDL, DCL, and DML in MySQL?

DDL means Data Definition Language that deals with database schemas as well as database description of how data can be stored in a database. One of the common examples of DDL is the “CREATE TABLE” command. DML means Data Manipulation Language that includes commands like SELECT, INSERT, etc. DCL means Data Control Language that includes commands like GRANT, REVOKE, etc.

Q50). What is the process to reset the password if the root password is lost in MySQL? 

If you have lost the root password in MySQL and need to regain access, you can follow these steps:  Stop the MySQL server. Start the MySQL server with the --skip-grant-tables option to bypass the password authentication. Connect to the MySQL server using the MySQL command-line client without providing a password. Update the root user's password using the UPDATE statement, ensuring you specify a strong and secure password. 

• Stop the MySQL server again. 
• Start the MySQL server normally without the --skip-grant-tables option. 

You should now be able to connect to the MySQL server using the new root password. It's important to note that resetting the root password should only be done if you have lost access to the existing password or if security has been compromised. Proper security measures should be in place to protect the MySQL server and sensitive data.  

Q51). How to compare transaction and ACID properties?

A transaction is a logical unit of work where all or none of the steps are performed. ACID means Atomicity, Consistency, Isolation, and Durability that can be defined as properties of a transaction.

Q52). What is the basic MySQL architecture?

The logical MySQL architecture is composed of a query optimizer, connection manager, and pluggable engines, etc.

Q53). How can tables be copied in SQL?

In SQL, it's occasionally necessary to make an exact duplicate of a defined or created table. You can execute this action using MySQL. Because we might require such backup tables to test the data without affecting the original table or the data contained within.

Create a table with the contacts (clone 1) similar to Original table; 

Q54). What is a Live Lock?

When two or more processes repeatedly interact in reaction to changes in the other processes without accomplishing any productive work, this is known as a "livelock." These processes are running simultaneously and are not in the waiting state. Deadlocks are distinct from this since all processes are in the waiting state. It is one of the frequently asked database developer interview questions that you should not miss. 

Q55). What do ACID characteristics entail?

A database's contents can be accessed and possibly modified as part of a single logical unit of work known as a transaction. Read and write operations are used by transactions to access data. Some attributes are followed before and after the transaction in order to preserve consistency in a database. We refer to these as ACID characteristics.

Q56). What does SQL ETL mean?

ETL stands for Extract, Transform, and Load and is a Data Warehousing method. Data is extracted from various data source systems using an ETL tool, transformed in the staging area, and then loaded into the Data Warehouse system. These three database operations are combined into one tool to extract data from a single database and to put data into another database.

Q57). Nested triggers are what?

A trigger can also include INSERT, UPDATE, and DELETE logic, which means that when it is activated due to a data alteration, it may also result in the activation of another trigger by causing yet another data modification. A nested trigger is one that includes data modification logic within itself. 

Q58). How can I access a table's available constraint information?

The data dictionary in SQL Server is a collection of database tables used to contain details about the definition of a database. These data dictionaries can be used to check and modify the constraints on a table that already exists (if possible).

Q59). What are the nonstandard string types?

Following are Non-Standard string types:

• TINYTEXT
• TEXT
• MEDIUMTEXT
• LONGTEXT

It is one of the frequently asked database developer interview questions that you should not miss.

Q60). What are all the Common SQL Function?

• CONCAT(A, B) – Concatenates two string values to create a single string output. Often used to combine two or more fields into one single field.
• FORMAT(X, D) – Formats the number X to D significant digits.
• CURRDATE(), CURRTIME() – Returns the current date or time.
• NOW() – Returns the current date and time as one value.

Q61). Where will the MyISAM table be kept, and what storage types are used there?

Three formats are used to store a MyISAM table on a hard drive:

• The table definition is kept in the ".frm" file.
• The data file's extension is ".MYD" (MYData).
• The index file's extension is ".MYI" (MYIndex).

This is how you can answer these types of SQL coding interview questions.

Q62). What distinguishes mysql fetch object from mysql fetch array?

Mysql fetch object and mysql interval fetch array differ in the ways listed below:

With the mysql fetch array() function, a result row can be returned from the database as an associated array or a standard array.

mysql fetch object - Retrieves a result row from the database as an object.

Q63). What distinguishes FLOAT and DOUBLE from one another?

FLOAT allocates 4 bytes and saves floating-point integers with an accuracy of up to 8 places. Yet, DOUBLE allocates 8 bytes and saves floating-point values accurately to 18 places. Focus on practicing to be prepared for such SQL join interview questions. 

Q64). What benefits does MyISAM have over InnoDB?

Each MyISAM table is stored separately in a file by MyISAM, which takes a conservative approach to managing disc space and can be further compressed if necessary. The tables are kept in the tablespace by InnoDB, on the other hand. Furthering its optimization is challenging.

Q65). How can a MySQL database be backed up?

With phpMyAdmin, data backup is simple. By choosing the database name in the left-hand navigation bar, choose the database you wish to backup. If all of the tables you want to backup are highlighted, click the export option. After that, choose the desired option under "export" and save the results. This is how you can answer these types of SQL coding interview questions.

Q66). What function do ENUMs provide in MySQL?

String objects are ENUMs. By establishing ENUMs, we enable the end-user to submit accurate input because if the user enters data that is not included in the ENUM specified data, the query will not run and an error message stating "The incorrect Query" will be presented. Make sure to include such topics in your SQL query practice.   

For instance, if we provide ENUM('male', 'female', 'other') to take the user's gender as an input, any attempt by the user to enter a string other than one of these three will fail.

Q67). What command is used in MySQL to inspect the contents of a table?

To see the contents of the table in MySQL interval, use the SELECT command.  It is one of the frequently asked database developer interview questions that you should not miss.  This is how you can answer these types of SQL coding interview questions.

Q68). Explain Access Control Lists.

A set of permissions connected to an object is known as an ACL. Every time a user attempts to authenticate or run a command, MySQL verifies the permissions needed for the object, and if the permissions are available, execution succeeds. MySQL stores the Access Control Lists cached in memory.

Q69). What does a join in MySQL mean?

Use joins in MySQL to query data from two or more tables. The query is built using the connections between a few table columns. There are four distinct join types in the MySQL interval.

An inner join produces rows if there is at least one match in both tables. A left join still returns every row from the left table even if there is no match in the right table. A right join still returns all the rows from the right table even if there are no matches in the left table. A full join would result in rows being returned if there is at least one match between the tables. Make sure to include such topics in your SQL query practice. 

Q70) What is a relational database?

A relational database is a type of database that uses a structured approach to store and manage data in tables with rows and columns. It establishes relationships between tables, allowing for efficient data retrieval and organization.

Q71) Explain normalization in the context of databases.

Normalization is the process of organizing data in a database to reduce data redundancy and improve data integrity. It involves breaking down large tables into smaller, related tables and defining relationships between them.

Q72) What is an Index in MySQL?

An index is a database structure that improves the speed of data retrieval operations on a table. It allows MySQL to find and retrieve data more quickly by creating a sorted list of values from one or more columns.

Q73) What is ACID? What does the component C in ACID mean?

ACID are key properties of database transactions in MySQL. It is an acronym that stands for Atomicity, Consistency, Isolation, and Durability.

The C component stands for consistency. According to this property, MySQL ensures that a transaction takes the database from one consistent state to another.

Q74) What is the purpose of the stored procedure in MySQL?

A stored procedure is a precompiled SQL statement that can be executed within the database. It allows for better code organization, reusability, and improved security.

Q75) What is the role of the MySQL JOIN clause in a query, and what are some common types of joins?

The role of the JOIN clause is to combine rows from two or more tables based on a related column between them.

Why Learn MySQL?

Learning MySQL offers a variety of benefits and prospects. It is a significant ability in the labor market since it is extensively utilized around the world. An effective relational database management system (RDBMS) called MySQL makes it possible to create scalable and well-organized applications by handling structured data with efficiency. It is adaptable and works with a wide range of programming languages and operating systems. Since MySQL is an open-source solution, there are no license fees, which makes it more affordable.

You might want to look at this MySQL certification to grasp a better hold in this field. 

Large datasets may be handled by it because of its famous outstanding performance and scalability. Developing MySQL skills improves employability and provides a variety of employment options in the data-driven sector. 

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SQL Courses	Course link
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SSAS Training Course	https://www.janbasktraining.com/sql-server-analysis-services

Final Thoughts

So, whether you have intermediate or expert SQL skills, these top MySQL interview questions and answers were chosen after extensive study to be acceptable for every applicant seeking a job in the database field. 

We hope this collection of MySQL interview questions has provided you with the necessary information to ace your next MySQL interview since typically, every job interview conversation starts with the fundamentals and progresses to the advanced level. Join JanBask Training's online SQL training to further your profession by adding a certification to your CV. 

Do you have any questions regarding MySQL interviews or uncertainty about the career path? Leave your MySQL interview questions or any additional MySQL interview questions in the comments box, and our experts will get back to you right away with answers! 

FAQ’s

Question 1: What Are Some Commonly Asked Mysql Interview Questions for Experienced Candidates?

Answer: Experienced candidates might face MySQL query interview questions on advanced topics such as database normalization, query optimization techniques, stored procedures, triggers, and indexing strategies. Mysql interview questions and answers for experienced users may also be asked to demonstrate their problem-solving skills through real-world scenarios or performance-tuning exercises.

Question 2: Can You Explain the Difference Between Mysql and MS SQL?

Answer: MySQL and MS SQL (Microsoft SQL Server) are both popular relational database management systems. While MySQL and MS SQL training share some similarities, there are notable differences. MySQL is open-source and free, widely used in web development, and known for its speed and simplicity. MS SQL is a commercial product with more advanced features, and better integration with Microsoft technologies, and is commonly used in enterprise environments.

Question 3: What Is the Purpose of the Group by Clause in Mysql?

Answer: The GROUP BY clause in MySQL is used to group rows based on one or more columns. It is often used in combination with aggregate functions like SUM, COUNT, AVG, etc., to perform calculations on groups of rows rather than individual rows. This allows for data analysis and reporting at a higher level of granularity.

Question 4: What Are SQL Certificate Courses and How Can They Benefit a Professional’s Career?

Answer: SQL certificate courses, such as MS SQL certification, validate an individual's knowledge and skills in working with SQL databases. Microsoft SQL server certification demonstrates expertise in areas like database design, querying, administration, and optimization. SQL certifications can enhance job prospects, increase earning potential, and provide a competitive edge in the job market for professionals seeking roles related to database management and development.

Question 5: Can You Explain the Concept of Transaction in Mysql?

Answer: A transaction in MySQL is a sequence of database operations that are treated as a single logical unit. It follows the ACID (Atomicity, Consistency, Isolation, Durability) properties. Transactions allow multiple database operations to be executed together, ensuring data integrity and consistency. In case of any errors or failures, a transaction can be rolled back to its original state using the ROLLBACK command.