51 MySQL Interview Questions You Need to Know in 2022
Prepare yourself for any interview with these basic, intermediate, and advanced MySQL interview questions. Even if you’re already pretty experienced with MySQL, you might not know everything there is to know — or everything that an interviewer might ask you about. We’ve compiled a complete list of the most common MySQL interview questions that interviewers ask.
Why do you need to know these MySQL interview questions?
Not only can these interview questions help you ace an interview, but they can also help you with a MySQL certification exam. MySQL interview questions give you insights not only into what you do know but what you don’t know — what are areas that you need to brush up on? Through MySQL interview questions, you can determine, for instance, that you need to know more about MySQL Workbench or that you need to know more about INNER JOIN functions.
Usually, MySQL interview questions are used so that an interviewer can determine how skilled you are with MySQL and if there appear to be any gaps in your knowledge. The more you practice, the better your results will be.
Basic MySQL interview questions
These questions are questions that you should know the answer to if you have just a little experience in MySQL. If you’re interviewing for an entry-level position, you should know the answers to these questions. These may also have some overlap with general SQL interview questions.
1. What is MySQL?
MySQL is a relational database management system as well as a popular choice for web applications used by millions of websites. It is produced by MySQL AB, which Oracle Corporation now owns.
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2. What is the difference between MySQL and SQL?
MySQL is a database management system, while SQL is the standard database query language. MySQL includes an SQL interpreter, while SQL queries can also be run on other database management systems.
3. What is the difference between a database and a table?
A database is a collection of tables, while a table is a collection of data. A table consists of rows and columns, and each row represents a record in the table. A column represents a field in the table, and each field has a specific type of data. For example, a column might store a person’s name, while another column might store the person’s age.
4. What is MySQL Workbench?
MySQL Workbench is a visual database management system. Not everyone wants to use MySQL in the command line, typing out all the commands; some people want a visual interface for MySQL. The MySQL Workbench lets you point-and-click your way through databases and tables.
5. What is the LAMP Stack?
The LAMP stack refers to a technology stack used for rapid web deployment of a MySQL server. It includes the Linux operating system, Apache web server, MySQL database, and PHP programming language.
6. What’s the difference between CHAR and VARCHAR?
CHAR is a data type used to store fixed-length character data, while VARCHAR is used to store variable-length character data. The maximum length for CHAR is 255 characters, while the maximum length for VARCHAR is 2,000 characters.
7. What is the difference between an INT and a FLOAT?
INT is a data type used to store integer values, while FLOAT is used to store floating-point values. An INT would be a number like 3, whereas a FLOAT would be a number like 3.0.
8. Is MySQL case sensitive?
Yes, MySQL is case-sensitive. This means that the values ‘hello’ and ‘Hello’ are different and would be stored as different values in MySQL. However, when it comes to the commands that you type into the command line, those can be in any case.
9. What type of database is MySQL?
MySQL can handle up to 50 concurrent connections. However, this number may be lower if you are using InnoDB tables. Additionally, you can use the max_connections variable to change the maximum number of concurrent connections that MySQL will allow.
10. How do you insert data into a MySQL table?
You can insert data into a MySQL table like so:
|INSERT INTO users (name, email) VALUES (‘John’,’[email protected]’);|
As you can see, you outline the column names and then the values.
11. How do you delete data from MySQL?
You can delete data from MySQL as follows:
|DELETE FROM users WHERE name = ‘John’;|
This would delete any records in which the name was “John.”
12. How do you update data in MySQL?
You can update data from MySQL as follows:
|UPDATE users SET name = ‘Johnathan’ where name = ‘John’;|
This would update any records in which the name was “John” to “Johnathan.”
13. What is a key in MySQL?
A key refers to an identifier that can be used to pull records. A primary key is usually a unique, numbered key. But a primary key could also be something like an email address, provided that it is known that there cannot be repeats of email addresses.
Intermediate MySQL Interview Questions
If you’ve spent some time learning MySQL and exploring its use, then you should be able to answer intermediate MySQL questions. These are questions that you can expect to be asked if a job requires a lot of work in or with MySQL.
14. What is the LIKE statement?
The LIKE statement and % wildcards make it possible to SELECT, UPDATE, and DELETE imprecise matches. For instance:
|SELECT * FROM users WHERE NAME LIKE = “J%”;|
This would select all the users with names that start with J.
|SELECT * FROM users WHERE NAME LIKE = “%e”;|
This would select all users with names that end with e.
15. Can you save images in MySQL?
Yes. You can save images directly in MySQL as “blobs.” But this isn’t ideal. Blobs are very large and will bog down the system. It’s better to store a URL of an image and then store the image itself separately on the server.
16. What are foreign keys?
When you connect multiple tables, you use foreign keys. In the tables that you’re connecting, these foreign keys are the primary keys, so this is a way to join multiple tables for the purposes of updating and selecting data.
17. What is MyISAM?
MyISAM refers to the storage engine of MySQL or where the data is actually stored. A MyISAM table can store up to 256 terabytes of information, although the system performance at that point would be heavily based on the technology of the server rather than MySQL itself.
18. What are the advantages of using the MySQL SQL server?
Some benefits of using MySQL include its reliability, scalability, and wide range of features. It is also a popular choice for web applications as it is fast and easy to use. It’s open source, so you can download it for free any time, and it has a very active and vibrant community.
19. What is the difference between a LEFT JOIN and a RIGHT JOIN?
A LEFT JOIN will return all the records from the left table, even if there aren’t any matches in the right table. A RIGHT JOIN will return all the records from the right table, even if there are no matches in the left table.
20. How do you export a MySQL database?
The easiest way to export a database is through the MySQL DUMP command.
|MYSQLDUMP database_name > backup.sql|
This will export all of the data in database_name to backup.sql. It’s important to note that the way this is stored is in a file that essentially reconstructions the database from scratch.
21. How do you import a MySQL database?
To import a MySQL database, you would use the MySQL DUMP command.
|MYSQLDUMP database_name < backup.sql|
This will run all the data that is stored in the SQL file.
22. How do you add users in MySQL?
To add a user in MySQL, you can use the CREATE USER statement. For example:
|CREATE USER ‘new_user’@’localhost’ IDENTIFIED BY ‘new_password’;|
You can also use the GRANT statement to give a user access to specific databases or tables.
23. How can you check users in MySQL?
Use the command:
|SELECT USER from mysql.user;|
This will list all users in MySQL.
24. How can you check the version of MySQL?
You can check the current version of MySQL by running the following command:
This might throw you off because -v is the “verbose” flag (which gives additional information about commands) traditionally under Linux and Unix environments.
25. How can you change a MySQL password?
If you need to change your MySQL password, you can use the following command:
|mysql -u username -p|
You will be prompted to enter in your old password, and then you’ll be asked for your new password.
You can also update a mysql.user record and set the identification to PASSWORD(“new_password”).
26. How do you create a database?
To create a database in MySQL, you can use the following command:
|CREATE DATABASE new_database;|
You will then need to USE the database.
27. How do you create a database in MySQL Workbench?
Go to File -> Create Schema. You will then be walked through the process of creating your new database, which will be empty until you’ve created the appropriate schema.
28. How do you change a table name?
You change a table name through the RENAME function. It’s very easy:
|RENAME table_1 TO table_2;|
This will rename table_1 to table_2.
29. How do you change a database name?
You cannot change a database name. What you can do is export the data from the database, create a new database, upload the data into that database, and then delete the database.
30. How do you change a column name?
You will use the ALTER TABLE setting to change a column name:
|ALTER TABLE test_table CHANGE COLUMN column_1 column_2 varchar(255);|
The CHANGE COLUMN modifier of ALTER TABLE actually lets you change both the name of the column and its type. In the above, we set the name to column_2 and the type to varchar(255).
How do you get the current date in MySQL?
You would run the CURRENT_DATE() command. This is important because there are times when you might want to introduce a record that includes something like a timestamp.
31. How can you load a CSV into MySQL?
Use the LOAD command as follows:
|LOAD DATA INFILE ‘file.csv’ INTO TABLE table_name;|
You can also do things like ignore a certain amount of rows.
32. What are the disadvantages of MySQL?
One potential drawback of using MySQL is that it can be difficult to use for complex queries. It can also be slow when used with large datasets. MySQL also doesn’t have the customer support that other similar products do because it’s not a commercial product; it’s an open-source product that’s free to everyone.
Advanced MySQL Interview Questions
Advanced MySQL questions cover things that you should be expected to know if you’ve been working with MySQL for some time. But there are always situations that people just miss; there may be things that you haven’t had to learn about yet.
33. How would you add a column to a MySQL table?
If you’re trying to modify an existing table, you need to use the ALTER TABLE command:
|ALTER TABLE users ADD COLUMN email VARCHAR (255) AFTER name;|
The above code would add the column “email” to the “users” table after the column “name.”
34. How would you delete a column in a MySQL table?
To delete a column in a MySQL table, you would again use the ALTER TABLE command:
ALTER TABLE users DROP email;
The above would drop the email column This is very dangerous if you haven’t backed up your database.
35. How do you join tables in MySQL?
There are four ways to join tables in MySQL: LEFT JOIN, RIGHT JOIN, INNER JOIN, and CROSS JOIN.
The “INNER JOIN” keyword will only include data from the tables that have matching values in the specified column. The “LEFT JOIN” keyword will include data from the left table, even if there are no matching values in the right table. The “RIGHT JOIN” keyword will include data from the right table, even if there are no matching values in the left table.
A MySQL cross join will combine the data from two tables, and it will include a row in the output for every possible combination of values in the two tables. This is extremely resource-intensive.
36. Can the primary key of a table be dropped?
MySQL will not stop you from dropping the primary key of a table. But it’s not a good idea; it will make it very difficult to manipulate the table. On the other hand, you can also add the primary key again or set another column to be the unique ID.
37. Does a primary key need to be a unique ID?
A primary key must be unique and cannot be null. To ensure this, flag the primary key with “auto_increment.”
38. What is DISTINCT in MySQL?
Distinct is a method for pulling records that ensures that records aren’t repeated. If you need each record only a single time, DISTINCT is important. DISTINCT can be especially useful if you are joining multiple tables in a way that records might be multiplied.
39. What is the difference between mysql_connect and mysql_pconnect?
mysql_connect() is used to connect to a MySQL server. mysql_pconnect() is used to connect to a MySQL server and keep the connection open for future use.
40. What language is MySQL written in?
MySQL was written in C/C++. But you should never need to modify the code of MySQL, although since it is open source, you could.
41. What is a stored procedure?
A stored procedure is essentially the MySQL version of a macro. You can use CREATE PROCEDURE to declare a sequence of SQL statements that you want to run every time that procedure is run. To run the stored procedure, use CALL.
42. What is a view in MySQL?
A view is a virtual table that’s built out of other data, intended to make it easier to pull specific data from a table or multiple tables on command rather than having to individually build that table out through SELECT statements each time.
43. How do you create a trigger in MySQL?
You use the CREATE TRIGGER command in MySQL to trigger certain actions. For instance, you could trigger a specific action whenever something is updated on a table, deleted from a table, or inserted into the table.
44. When can triggers be used in MySQL?
Triggers can be used before or after an insert, before or after an update, before or after a delete. These are the only types that triggers can be used in MySQL. If you are asked how many triggers there are, there are six total.
45. How do you clear the screen in MySQL?
The SYSTEM CLS command will clear the screen so you can better differentiate new results from the old results.
46. What is the difference between MySQL Community and MySQL Enterprise?
The MySQL Community edition is a freely available version of the MySQL database server. It is licensed under the GPL, and is supported by a large community of users and developers.
The MySQL Enterprise edition is a commercial version of the MySQL database server. It is licensed under a proprietary license and is supported by a team of paid employees.
47. What is the InnoDB storage engine?
The InnoDB storage engine is used for storing data in tables. It provides features such as transactions, foreign keys, and row-level locking.
48. What are the differences between MyISAM and InnoDB?
MyISAM is a storage engine that is commonly used for storing data in tables. InnoDB is a more advanced storage engine that provides features such as transactions and rollbacks…but it can also be more challenging to use.
49. What are the benefits of using InnoDB?
The benefits of using InnoDB include:
- Transactions: InnoDB provides transactions, which allow multiple statements to be grouped into a single logical unit of work. This helps ensure the integrity of the data in the database.
- Foreign Keys: InnoDB supports foreign keys, which allow you to enforce referential integrity between tables. This means you can guarantee that the data in one table is consistent with the data in another table.
- Row-level Locking: InnoDB uses row-level locking, which helps to ensure that only one user can access a particular row of data at a time. This helps to prevent data from being corrupted or updated incorrectly.
Most applications will not require these features, but if a company deals with currencies or financial documents, they may use InnoDB.
50. What is a clustered index?
A clustered index is a type of index that is used to organize data in a table. The clustered index determines the order in which the data is stored in the table.
51. What is a non-clustered index?
A non-clustered index is a type of index that is used to organize data in a table. The non-clustered index does not determine the order in which the data is stored in the table.
Tips for Winning Your Next MySQL Interview
So, you’re heading into an interview. What do you need to know next? Here are some important tips for remaining confident and collected.
- Don’t be afraid to admit you don’t know something. Turn it around to what you do know and what you suspect. It’s better to admit that you need to learn than try to pretend.
- Remember that MySQL isn’t SQL. The interview will be about MySQL specifically. Don’t spend all your time learning the language. Also, learn about Workbench, mysqladmin, and command line commands.
- Simulate different environments. In your spare time, build databases for different applications; this will introduce you to a different subset of problems each time.
- Be prepared to answer questions about your experience with MySQL. What kind of projects have you used it on? What types of queries are you familiar with? How comfortable are you working with databases in general?
- Be ready to answer questions about your understanding of the MySQL licensing model. Are you familiar with the Community and Enterprise editions, and what are the key differences between them?
MySQL is a complex solution. While you can hit the ground running with it, it can take years to master. Spend some time digging deeper into MySQL projects and practicing different application types.
You don’t need to memorize all the MySQL data types, SQL commands, or SQL statements to ace an interview. But you do need to have a reasonable amount of experience in MySQL. The best way to prepare for a MySQL interview is to review and expand your knowledge with more MySQL Courses. Learn more about what you don’t know about, and practice developing applications in MySQL.
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