MySQL (DBA) Basic Interview Question with Answer - Part 1

Here are some commonly asked MySQL interview questions along with their answers:

1. What is MySQL?

MySQL is a popular open-source relational database management system. It uses SQL (Structured Query Language) to manage data and is used for a variety of applications, including web applications, content management systems, and e-commerce sites.

2. What is the difference between MySQL and SQL Server?

MySQL and SQL Server are both relational database management systems, but they are developed by different companies and have different features. MySQL is open source, while SQL Server is a proprietary software developed by Microsoft. MySQL is often used for web-based applications and is known for its scalability, whereas SQL Server is known for its performance and enterprise-level features.

3. What are the different types of storage engines in MySQL?

MySQL supports different storage engines, which are responsible for storing and retrieving data. Some of the popular storage engines in MySQL are InnoDB, MyISAM, Memory, CSV, and Archive.

4. What is a primary key in MySQL?

A primary key is a column or a set of columns in a table that uniquely identifies each row in the table. It is used to enforce data integrity and ensure that each row has a unique identifier. In MySQL, a primary key can be defined using the PRIMARY KEY keyword while creating a table.

5. What is a foreign key in MySQL?

A foreign key is a column or a set of columns in a table that refers to the primary key of another table. It is used to establish a relationship between two tables and ensure referential integrity. In MySQL, a foreign key can be defined using the FOREIGN KEY keyword while creating a table.

6. What is a stored procedure in MySQL?

A stored procedure is a precompiled SQL statement that is stored in the database server and can be called by other programs or SQL statements. It is used to encapsulate complex SQL logic and improve performance by reducing network traffic between the client and server. In MySQL, a stored procedure can be created using the CREATE PROCEDURE statement.

7. What is a trigger in MySQL?

A trigger is a set of SQL statements that are automatically executed in response to certain events, such as insert, update, or delete operations on a table. It is used to enforce data integrity and implement complex business logic. In MySQL, a trigger can be created using the CREATE TRIGGER statement.

8. What is a view in MySQL?

A view is a virtual table that is based on the result of a SQL query. It does not contain any data itself but provides a way to access and manipulate data from one or more tables. In MySQL, a view can be created using the CREATE VIEW statement.

9. What is normalization in MySQL?

Normalization is the process of organizing data in a database to reduce redundancy and improve data integrity. It involves breaking down a large table into smaller tables and establishing relationships between them using primary and foreign keys. Normalization is important for efficient storage, retrieval, and manipulation of data in a database.

10. What is indexing in MySQL?

Indexing is the process of creating an index on a table to improve query performance. It involves creating a data structure that stores a reference to each row in the table based on the values in one or more columns. Indexing is important for fast retrieval of data from a large table. In MySQL, an index can be created using the CREATE INDEX statement.

11. What is the difference between CHAR and VARCHAR data types in MySQL?

CHAR and VARCHAR are both character data types in MySQL. The main difference between them is that CHAR is fixed-length and VARCHAR is variable-length. This means that a CHAR column always uses the same amount of storage, while a VARCHAR column can use up to the specified maximum length.

12. What is the difference between GROUP BY and ORDER BY in MySQL?

GROUP BY and ORDER BY are both clauses used in MySQL queries. GROUP BY is used to group the results of a query by one or more columns, while ORDER BY is used to sort the results of a query by one or more columns. The main difference is that GROUP BY aggregates the data and returns a summary of the results, while ORDER BY simply sorts the data.

13. What is a subquery in MySQL?

A subquery is a query that is nested inside another query. It is used to retrieve data from one or more tables based on the results of another query. Subqueries can be used in SELECT, INSERT, UPDATE, and DELETE statements in MySQL.

14. What is the difference between a left join and an inner join in MySQL?

Both left join and inner join are types of joins in MySQL. The main difference between them is that a left join returns all the rows from the left table and matching rows from the right table, while an inner join only returns the matching rows from both tables.

15. What is a transaction in MySQL?

A transaction is a sequence of SQL statements that are executed as a single unit of work. Transactions are used to ensure data integrity and consistency by guaranteeing that either all the statements in a transaction are executed successfully, or none of them are executed at all. Transactions can be started using the BEGIN statement and ended using either the COMMIT or ROLLBACK statement.

16. What is the difference between the LIKE and = operators in MySQL?

The LIKE and = operators are both used to compare values in MySQL. The main difference between them is that the LIKE operator can be used to match patterns, while the = operator only matches exact values. For example, the LIKE operator can be used to search for values that contain a specific substring, while the = operator can only be used to search for exact matches.

17. What is the difference between a primary key and a unique key in MySQL?

Both primary key and unique key are used to ensure data integrity in MySQL. The main difference between them is that a primary key is used to uniquely identify each row in a table, while a unique key is used to ensure that no two rows have the same value for a specific column or set of columns.

18. What is a full-text index in MySQL?

A full-text index is a type of index that is used to search for text-based data in MySQL. It is designed to support natural language search queries and can be used to search for words or phrases within a column. Full-text indexing can be enabled using the FULLTEXT keyword when creating a table.

19. What is a cursor in MySQL?

A cursor is a database object that is used to traverse the results of a query one row at a time. It is often used in stored procedures and triggers to perform complex data manipulation tasks. Cursors can be defined using the DECLARE CURSOR statement in MySQL.

20. What is the purpose of the EXPLAIN statement in MySQL?

        The EXPLAIN statement is used to analyze the execution plan of a SELECT statement in MySQL. It             provides information about how the database will execute the query, including which indexes will be             used, the order of table joins, and the estimated number of rows that will be returned. This information         can be used to optimize the performance of the query. 

MySQL (DBA) Basic Interview Question with Answer - Part 2