Top 27 MySQL Interview Questions & Answers For Beginners & Experienced [2023]

Have a Data engineering or data science interview coming up? Need to practice some of the most asked MySQL interview questions? The article compiles the list of the MySQL interview questions that you should know.

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Common MySQL Interview Questions & Answers

1. What is MySQL?

MySQL is one of the most popular open-source DBMS (database management system). MySQL is easy to use, reliable, and fast. A DB management system that works on embedded systems as well as client-server systems. 

2. Why is MySQL so popular? 

First of all, MySQL is open-source. Second, it is widely adopted, so a lot of code is already available. Even entire developed systems are there that can be referred to for the upcoming projects. MySQL has relational databases; hence it makes it have methodical storage rather than a big dump of unorganized mess. And finally, as said earlier, MySQL is quick and robust. 

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3. What are the tables in MySQL? Explain the types.

This is a must-know MySQL interview question. Let’s see the answer-

MySQL stores everything in logical tables. Tables can be thought of as the core storage structure of MySQL. And hence tables are also known as storage engines. Here are the storage engines provided by MySQL:

· MyISAM – MyISAM is the default storage engine for MySQL. It extends the former ISAM storage engine. MyISAM offers big storage, up to 256TB! The tables can also be compressed to get extra storage. MyISAM tables are not transaction-safe. 

· MERGE – A MERGE table is a virtual table that consolidates different MyISAM tables that have a comparable structure to one table. MERGE tables use the indexes of the base tables, as they do not have indexes of their own.

· ARCHIVE – As the name suggests, Archive helps in archiving the tables by compressing them, in-turn reducing the storage space. Hence, you can store a lot of records with the Archive. It uses the compression-decompression procedure while writing and reading the table records. It is done using the Zlib library.

· CSV – This is more like a storage format. CSV engine stores the values in the Comma-separated values (CSV) format. This engine makes it easier to migrate the tables into a non-SQL pipeline.

· InnoDB – InnoDB is the most optimal while choosing an engine to drive performance. InnoDB is a transaction-safe engine. Hence it is ACID-compliant and can efficiently restore your database to the most stable state in case of a crash.

· Memory– Memory tables were formerly known as HEAP. With memory tables, there can be a performance boost as the tables are stored in the memory. But it does not work with large data tables due to the same reason.

· Federated – Federated tables allow accessing remote MySQL server tables. It can be done without any third-party integration or cluster technology.

Read: SQL for Data Science: Why SQL, List of Benefits & Commands

4. Write a query for a column addition in MySQL

This is one of the significant MySQL query interview questions. For this, an ALTER TABLE query is required. Once invoked, simply mention the column and its definition. Something like this:

ALTER TABLE cars

ADD COLUMN engine VARCHAR(80) AFTER colour;

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5. What is a foreign key? Write a query to implement the same in MySQL.

This is one of the prevalent MySQL queries interview questions for both beginner and experienced candidates. A foreign key is used to connect two tables. A FOREIGN KEY is a field (or assortment of it) in one table that alludes to the PRIMARY KEY in another table. The FOREIGN KEY requirement is utilised to forestall activities that would crush joins between tables.

To assign a foreign key, it is important to mention it while creating the table. It can be assigned by invoking the FOREIGN KEY query. Something like this:

FOREIGN KEY (Any_ID) REFERENCES Table_to_reference(Any_ID)

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6. What is MySQL workbench?

MySQL Workbench is a bound together visual instrument for database modelers, designers, and DBAs. MySQL Workbench provides Data modelling, SQL, and server setup set of administrative tools. To put it simply, MySQL workbench makes it possible to operate the database management system through GUI. 

7. How does database import/export work in MySQL?

It can be done in two ways. One is to use phpMyAdmin, and the second is to use the command line access of MySQL. The latter can be done by using the command named mysqldump. It goes something like this:

· mysqldump -u username -p databasename > dbsample.sql

To import a database into MySQL, only a sign change is required, with a command of MySQL. The command goes something like this:

· mysql -u username -p databasename < dbsample.sql

8. How can we delete a column or a row in MySQL?

Now dropping a column can be simply done by using the ALTER TABLE command and then using the DROP command. It goes something like this:

ALTER TABLE table_name DROP column name;

To drop a row, first, an identification for the row is required. Once that is handy, use the DELETE command in conjunction with the conditional WHERE command. Something like this:

DELETE FROM cars WHERE carID = 3;

9. What are the different ways to join tables in MySQL?

This is one of the most important MySQL database interview questions.

Join is used to link one or more tables together, with the common column’s values in both tables. Primarily there are four types of joins:

1. Inner Join – Inner join uses a join predicate, which is a condition used to make the join. Here is the syntax:

SELECT something FROM tablename INNER JOIN another table ON condition;

2. Left Join – Left join also requires a join condition. The left join chooses information beginning from the left table. For each entry in the left table, the left compares each entry in the right table. Here is the syntax:

SELECT something FROM tablename LEFT JOIN another table ON condition;

3. Right Join – Opposite to left join and, with one difference in the query, that is the name of join. Here care should be taken about the order of tables. Here is the syntax:

SELECT something FROM tablename LEFT JOIN another table ON condition;

4. Cross Join – Cross join has no join condition. It makes a cartesian of rows of both the tables. Here is the syntax:

SELECT something FROM tablename CROSS JOIN another table;

Note: While dealing with just one table, self-join is also possible. 

It is one of the most dealt with MySQL interview questions. Interviewers do like to see if the candidate understands the basics or not and join one of the core concepts. 

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10. Can a primary key be dropped in MySQL? If yes, how?

Yes, it is possible to drop the primary key from a table. The command to use is again, the ALTER TABLE followed by DROP. It goes like this:

ALTER TABLE table_name DROP PRIMARY KEY;

11. What are Procedures in MySQL?

This is a MySQL basic interview questions. A thorough understanding of this is very important. 

Procedures (or stored procedures) are subprograms, just like in a regular language, embedded in the database. A stored procedure consists of a name, SQL statement(s) and parameters. It utilises the caching in MySQL and hence saves time and memory, just like the prepared statements. 

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12. What is a trigger in MySQL?

A trigger is a table-associated database object in MySQL. It is activated when a specified action takes place. 

A trigger can be invoked after or before the event takes place. It can be used on INSERT, DELETE, and UPDATE. It uses the respective syntax to define the triggers. For example, BEFORE INSERT, AFTER DELETE, etc.

13. How to add users in MySQL?

To simply put, the user can be added by using the CREATE command and specifying the necessary credentials. First, log in to the MySQL account and then apply the syntax. Something like this:

CREATE USER ‘testuser’ IDENTIFIED BY ‘sample password’;

Users can be granted permissions, by the following commands:

GRANT SELECT ON * . * TO ‘testuser’;

14. What is the core difference between Oracle and MySQL?

The core difference is that MySQL works on a single-model database. That means it can only work with one base structure, while Oracle is a multi-model database. It means it can support various data models like graph, document, key-value, etc. 

Another fundamental difference is that Oracle’s support comes with a price tag for industrial solutions. While MySQL is open-source.

Now this question is one of the MySQL interview questions that should be understood carefully. Because it directly deals with the industry standards and what the company wants.

MySQL is free and open-source, whereas Oracle is commercial and paid. MySQL is more customizable than Oracle because Oracle is a finished product.

From the software perspective, Oracle is more powerful owing to its extra features. Also, it offers better indexing due to which it provides a competitive benefit over MySQL.

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15. What is CHAR and VARCHAR in MySQL?

This is one of the most important interview questions on MySQL. 

Both of them define a string. The core difference is that CHAR is a fixed-length while VARCHAR is variable length. For example, if CHAR(5) is defined, then it needs exactly five characters. If VARCHAR(5) is defined, then it can take at most five characters. VARCHAR can be said to have more efficiency in the usage of memory as it can have dynamic memory allocations. 

16. Which drivers are necessary for MySQL?

There are many types of drivers in MySQL. Mostly they are used for connections with different computational languages. Some of them are listed below:

· PHP Driver

· JDBC

· OBDC

· Python Driver

· C – Wrapper

· Perl and Ruby Drivers

17. What is a LIKE statement? Explain % and _ in LIKE.

While using filters in commands like SELECT, UPDATE, and DELETE, conditions might require a pattern to detect. LIKE is used to do just that. LIKE has two wildcard characters, namely % (percentage) and _ (underscore). Percentage(%) matches a string of characters, while underscore matches a single character. 

For example, %t will detect trees and tea both. However, _t will only detect one extra character, i.e., strings like ti or te. 

18. How to convert timestamps to date in MySQL?

It is a rather simple question that requires knowledge on two commands, like DATE_FORMAT and FROM_UNIXTIME. 

DATE_FORMAT(FROM_UNIXTIME(`date_in_timestamp`), ‘%e %b %Y’) AS ‘date_formatted’

Also Read: Java Interview Questions & Answers

19. Can a query be written in any case in MySQL?

This MySQL interview question often confuses people who are just getting started with MySQL. Although most of the time, the queries are written in capital or some in small letters, there is no such case sensitivity to MySQL queries. 

For example, both create table tablename and CREATE TABLE tablename, works fine.

However, if required, it is possible to make the query case sensitive by using the keyword BINARY. 

This MySQL interview question can be tricky, especially when asked to make the query case-sensitive explicitly. 

20. How to save images in MySQL? 

This is one of the most basic MySQL interview questions. 

Images can be stored in the MySQL database by converting them to BLOBS. But it is not preferred due to the large overhead it creates. Plus, it puts unnecessary load on the RAM while loading the entire database. It is hence preferred to store the paths in the database and store the images on disk. 

21. How to get multiple condition results from data in MySQL?

There are two ways to do so. The first is to use the keyword OR while using the WHERE condition. The other is to use a list of values to check and use IN with WHERE. 

22. What are the different file formats used by MyISAM?

Typically, a MyISAM table is stored using three files on disk. The data file and the index file, which are defined with extensions .MYD and .MYI, respectively. There is a table definition file that has .frm extension. 

23. How does DISTINCT work in MySQL?

DISTINCT is used to avoid the problem of duplicity while fetching the results of a particular query. DISTINCT is used to make sure the results do not contain repeated values. DISTINCT can be used with the SELECT clause. Here is the syntax for it:

SELECT DISTINCT something FROM tablename;

24. Is there any upper limit for the number of columns in a table?

Although the exact size limitation depends on many factors, MySQL has a hard limit on max size to be 4096 columns. But as said, for a given table, the effective-maximum may be less.

25. What are Access Control Lists or ACLs, in accordance with MySQL?

The ACLs or Access control lists are used in a way to give a guideline for security in the MySQL database. MySQL provides security based on ACLs for all the tasks performed by users like connection requests, queries, and any other operation. 

26. How to make connections persistent in MySQL?

While making a connection request, if Mysql_pconnect is used rather than mysql_connect, then it can make the connection persistent. Here ‘p’ means persistent. The database connection is not closed every time.

27. Explain the SAVEPOINT statement in MySQL.

SAVEPOINT is a way of making sub-transactions in MySQL, which are also known as nested transactions. 

SAVEPOINT marks a point in a regular transaction. It indicates a point to which the system can rollback. 

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28. Can MySQL store images and videos?

This is one of the important MySQL interview questions. MySQL allows you to store binary content in a table with the help of VARBINARY or BINARY data type for a column. It can store file content like images, sound, videos, simply a binary snippet, etc. There are two methods to save images. The most widespread method is to save the file name in the MySQL table and then upload the image to the folder. The second method is to store the image in the database directly.

29. How does MySQL use indexes?

It is important to prepare for MySQL interview questions around indexes. MySQL use indexes to quickly find rows with specific column values. They are also used to eliminate the rows from consideration. When not using an index, MySQL should start with the first row and read through the whole table to find out the relevant rows. The bigger the table, the higher will be the costs. A table may have an index for columns in question. In such cases, MySQL can swiftly decide the position to find out in the data file’s centre without looking through all data. This process is quite faster than reading each row sequentially.

30. Why is MySQL better than other databases?

It is one of the fundamental MySQL interview questions and answers. MySQL is dominating the list of powerful transactional database engines on the market. The features like consistent, complete atomic, isolated, durable transaction support, multi-version transaction support, and unrestricted row-level locking make it the go-to solution for full data integrity. Moreover, it offers widespread support for all application development requirements. In the MySQL database, you can find support for stored procedures, functions, triggers, cursors, views, ANSI-standard SQL, and more. These types of MySQL interview questions and answers for freshers test your knowledge of trending technology and how up tp date you are with the market. 

31. Where does MySQL store passwords?

This is one of the important MySQL interview questions and answers from a user data security viewpoint. MySQL stored passwords in the user table in the MySQL system database. Operations that modify or assign passwords are allowed only to those users with the CREATE USER privilege or, otherwise, privileges for the MySQL database. The INSERT privilege is used to create new accounts, and the UPDATE privilege is used to change existing accounts.

32. Are MySQL and SQL servers the same?

No, MySQL and SQL servers are different. Both are relational database management systems, but they differ in terms of pricing, use cases, features, licensing advantages, and more. MySQL is offered through Oracle, whereas SQL Server is through Microsoft Corporation.

The SQL server is far more secure than the MySQL server from the data security viewpoint. In SQL, external processes such as third-party apps can’t directly access or control the data. On the other hand, in MySQL, you can easily control or change the database files in run time using the binaries. Make sure to prepare these comparison-based MySQL interview questions and answers for freshers.

33. Are MySQL databases encrypted?

This one is among the MySQL interview questions for experienced professionals. MySQL Enterprise TDE allows data-at-rest encryption by encrypting the database’s physical files. Data is automatically encrypted, in real-time, before writing to storage. It is then decrypted when data is read from storage. Consequently, malicious users and hackers can’t directly read sensitive data from database files. MySQL Enterprise Encryption permits your enterprise to secure data by blending private, public, and symmetric keys. These keys help to encrypt and decrypt data. The encrypted data is stored in MySQL using DSA, RSA, or DH encryption algorithms.

34. Can MySQL store JSON?

MySQL allows a native JSON (JavaScript Object Notation) data type being defined by RFC 7159. It provides efficient access to the data in JSON documents. One of the key benefits of the JSON data type over storing the JSON-format strings in a string column is the automatic validation of JSON documents saved in JSON columns. But invalid documents generate an error. JSON documents saved in JSON columns are transformed to an internal format that allows rapid read access to the document elements. You can consider this question when preparing MySQL interview questions for experienced candidates.

35. Why did MySQL shut down unexpectedly?

It is one of the popular MySQL interview questions for freshers. The cause of MySQL shutting down unexpectedly is “Error: MySQL Shutdown Unexpectedly” in XAMPP. The common reasons are missing files, corrupted files, wrong database shutdown, and port changes. The corrupted files in the MySQL/data folder cause MySQL to shut down unexpectedly when you run MySQL on a web server. You may encounter this error when launching the Apache module and Apache module.

36. Are MySQL and MariaDB the same?

It is among the common MySQL query interview questions for both freshers and experienced professionals. MySQL and MariaDB both employ standard SQL syntax. This syntax can be common table expressions, window functions, and JSON and geospatial functions. MariaDB adds the EXCEPT and INTERSECT set operators, linear regression functions, and many more.

MariaDB is faster than MySQL when performing replication or queries. So, MariaDB is a decent choice if you want a high-performance relational database solution. Moreover, MariaDB supports a concurrent number of connections without significant performance degradation.

37. Why is my MySQL not working?

You can consider this question when preparing for the MySQL interview questions for freshers. Two reasons why MySQL is not working are error (2002) and error (2003). The error (2002) “Can’t connect to …” typically means that zero MySQL servers are operating on the system. It may also mean that you are using the wrong TCP/IP port number or Unix socket file name when connecting to the server.

The error (2003) “Can’t connect to MySQL server on ‘server’ (10061)” implies that the network connection has been rejected. You must make sure that the MySQL server is running, the network connections are enabled, and the network port you defined is the one configured on the server. Also, you must check that the TCP/IP port being used has not been blocked by a port blocking service or a firewall.

38. When does MySQL lock tables?

These types of MySQL queries interview questions are frequently asked to check candidates’ MySQL competencies. lock mechanism restricts the illicit access of the data in a table. MySQL permits a client session to explicitly obtain a table lock to cooperate with other sessions to access the table’s data. MySQL permits table locking to stop unauthorized modification in the same table during a particular period.

A MySQL session can obtain or release locks on the table just for itself. Thus, one session can’t obtain or release the table locks for other sessions. You should have SELECT privileges and a TABLE LOCK for table locking.

Reasons Why MySQL is Always The Preferred Management System

Given just how much information we currently produce, it is simple to understand why reliable database structures are crucial in modern web development.  Organisations are collecting large volumes of qualitative and quantitative data, but they require trustworthy database software and systems to use this data as a competitive advantage. While there are several database management systems, MySQL has various benefits and is often the preferred choice for large organizations. If you are preparing for a MySQL interview reading fundamental concepts and other interview questions on MySQL, then you must also understand its advantages, as it is one of the most basic MySQL interview questions. 

• Easily Available – Digital companies and online platforms must be able to offer 24/7 services as they have a worldwide clientele. Accessibility is a key component of MySQL because of this. It uses various cluster servers and distributed database techniques to guarantee continuous uptime even during a breakdown. To guarantee that data is not lost, MySQL additionally makes use of several recovery techniques.
• Extremely Reliable – The main idea behind MySQL was speed. Additionally, it is renowned for its dependability as a database administrator, supported by a sizable programming community that has put the code through stringent testing. The ease of learning and using it is another advantage. Additionally, you can easily locate expert MySQL developers when you need them because the technology has been in existence for almost thirty years.
• Secure – This is frequently a significant factor for organisations as they have to preserve sensitive information and defend against cyber threats. To safeguard the integrity of all kinds of information, MySQL provides encryption using the Secure Sockets Layer (SSL) protocol, authentication plugins, data masking, and other levels of security. Additionally, a firewall that guards against online threats is included in MySQL.
• Compatible Database – This basically implies that the fundamental programme may be installed and used by anybody and that the code can be altered and customised by third persons. Advanced forms include tiered price structures that include more capability, capacity, and solutions.

A large number of systems, computer languages, and database architectures are very compatible with MySQL. DBMS alternatives, SQL and NoSQL databases are all included in this. Additionally, MySQL includes a wide range of database architecture and data modelling features like conceptual data models or logical data models. As a result, it becomes a straightforward and useful alternative for many enterprises, all while brushing aside concerns about becoming “locked in” to the system.

• Scalable – The MySQL store has to be scaled up as there is growth in data volumes. It must be able to handle the increased workload without suffering performance degradation. There are several techniques to scale MySQL, usually through duplication or clustering. It can support and process very big databases, although doing so is likely to slow it down. 

Some large companies that have used MySQL and have grown are LinkedIn, Pinterest, Quora, Shopify, Twitter, Uber, yelp, YouTube, and Tumblr. Knowing about these companies will help you answer MySQL basic interview questions. MySQL database interview questions are often tricky and confuse candidates. Make sure your preparation is strong enough to face these!

Conclusion

So, these were some MySQL interview questions. To know about the subject and other preparations, do visit upGrad courses and PG programs that help you in finding the right track and applications to boost your career. 

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