MySQL Interview Questions and Answers
As one of the world’s most-utilized relational database management systems, MySQL is an indispensable asset in today’s technology sector.
So that you’ll have everything you need for success at your upcoming interview, we have put together this extensive database of MySQL Questions for Interviews.
From basic to complex subjects, here you will find everything from the fundamentals up until it comes time for an exam!
So get prepared now, show your proficiency with MySQL!
1. What is SQL?
SQL, or Structured Query Language, manages and manipulates databases.
2. What is a database?
A database collects information or processed data that can be stored and accessed efficiently.
3. What are the types of SQL commands?
There are four types of SQL commands: data definition language (DDL), data manipulation language (DML), data control language (DCL), and transaction control language (TCL).
4. What is the purpose of DML commands?
Data manipulation language (DML) commands are used to access and manipulate data tables, allowing for actions like inserting, updating, and deleting data.
5. What is the insert multiple row statement in SQL?
The insert multiple row statement allows for multiple rows in a single insert statement at a time by grouping row values with open and close brackets and separating each row with a comma. This can be useful for reducing the time and hassle of specifying column names each time.
6. What is the purpose of DCL commands?
Data control language (DCL) commands are used to maintain database security, allowing for the control of access and permissions to the database.
7. What is the purpose of TCL commands?
Transaction control language (TCL) commands manage and execute database transactions, allowing for actions like committing and rolling back changes to the database.
8. What are some SQL commands used for data manipulation?
Some SQL commands used for data manipulation include INSERT, UPDATE, DELETE, and SELECT.
9. What are some SQL data types?
Some SQL data types include numeric, bit, float, Boolean, and string.
10. What is a foreign key in SQL?
A foreign key in SQL is a column or combination of columns used to establish and force a link between two tables to control data stored in the foreign key table. It must have a matching primary key or be null.
11. What are some SQL operators?
Some SQL operators include arithmetic, comparison, logical, bitwise, and set operators.
12. What is the purpose of using the SQL select statement?
The SQL select statement fetches data from a database table and returns it in a resultant table.
13. What is the having clause in SQL?
The having clause in SQL is used alongside group by clauses to filter results based on specific conditions. It is similar to where clauses, but where clauses cannot be used with aggregate functions like count, max, and sum.
14. What is the syntax for the SQL select statement?
The SQL select statement’s syntax is followed as a column from the table name, where you can see column names one, two, and several.
15. What is the purpose of using the SQL select condition?
The SQL select condition is used with various clauses, such as the where clause, to retrieve the selected data that follows a particular condition.
16. What is the add column operation in SQL Server?
The add column operation in SQL Server allows you to add new columns, modify existing columns, and drop unnecessary ones.
By using these commands, you can streamline your data management and enhance your database experience.
17. What is the purpose of using the SQL select date statement?
To retrieve the values of a particular date from a database.
18. What is a scale outer join statement?
A scale outer join statement returns all records in the left or right table.
19. What is the purpose of using the SQL insert statement?
The SQL insert statement is a widely used command in SQL Server that inserts one or more rows into a database table with specified table column values.
20. What is the syntax for deleting rows from a table in SQL?
The syntax for deleting rows from a table in SQL is “delete from table name where condition”.
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21. What are the different types of SQL keys?
There are various types of keys in SQL, such as primary key, supercritical, candidate key, alternate key, composite key, and key.
22. What are SQL keys?
SQL keys are essential in relational databases for identifying unique rows from tables. They are subsets of columns that allow a row to be uniquely identified.
These keys help manage large amounts of information stored across multiple tables, which may contain duplicate rows with redundant data.
23. What is the difference between primary and alternate keys in SQL?
Primary keys are unique identifiers for each row in a table and ensure that no two rows have the same value.
Alternate keys are subsets of candidate keys that can also uniquely identify rows in a table, but they are not chosen as the primary key.
24. What is a super key in SQL?
A super key combines all possible attributes, uniquely identifying rows or tuples in a table. It is a superset of primary, candidate, and alternate keys, with additional attributes not needed for unique identification.
25. What is a composite key in SQL?
A composite key combines two or more attributes, uniquely identifying a tuple in a table.
26. How is normalisation used in SQL?
Normalisation is a process that eliminates data redundancy and enhances data in relational databases. It is used in SQL to reduce data redundancy, improving the data distribution across the database.
27. What is the group by statement in SQL?
The group by statement in SQL groups identical rows using a specified condition, often with aggregate functions like count, average, minimum, maximum, and average.
28. What is the order by statement in SQL?
The order by statement in SQL sorts data in ascending or descending order, with the ASC keyword for ascending order and the DESC keyword for descending order.
29. What is the wire clause in SQL?
The wire clause in SQL specifies a condition while fetching data from more than one table or by joining multiple tables. It is used not only in the select statement but also in the update, delete, etc.
30. What are sub-queries in SQL?
Sub-queries in SQL execute queries dependent on the outcome of another query and fetch results without writing multiple queries.
31. How can sub-queries be used to update existing data?
Subqueries can be used to update existing data in SQL by using the update statement and the where clause to specify the conditions for the update.
32. What is the rollback command in SQL?
The rollback command in SQL allows the database to return to its previous state before committing. If an error occurs, the commit command is used to undo or revert the changes made to the database.
33. How is the SQL-like operator used in SQL?
The SQL-like operator in SQL searches for specific patterns in data and returns records that match the specified criteria.
The operator uses wildcards to match characters and can be used with the like operator to search for specific values.
34. What is the difference between a sub-query and a join?
A subquery is a query within another query, while a join is a way to combine data from two or more tables based on a standard column.
Subqueries filter or retrieve data from a single table, while joins combine data from multiple tables.
35. What is the purpose of MySQL?
MySQL is a popular open-source relational database management system used to manage and store data in databases.
36. What is an SQL view?
A SQL view is a virtual table that stores the result of a SQL query. It is similar to a relational database table and allows users to view and manipulate data stored in the underlying SQL query.
37. What is the primary purpose of using a SQL view?
The primary purpose of using an SQL view is to provide a simplified way of accessing and manipulating data stored in the underlying SQL query. Views can also enhance data security, reduce complexity, and maintain data integrity.
38. What is the difference between a SQL view and a stored procedure?
A SQL view is a virtual table that stores the result of a SQL query, while a stored procedure is a precompiled SQL query that can be executed multiple times with different parameters.
39. How can a tuple be deleted from a table in SQL?
To delete a tuple from a table in SQL, use “delete” from the tables.
40. What is the purpose of using SQL views for data security?
SQL views can be used for data security because they allow you to hide or show data based on requirements and security. What is the difference between a SQL view and a table alias?
41. What is the purpose of using SQL views for data integrity?
SQL views can be used to maintain data integrity because they provide a consistent and accurate view of the underlying data.
42. How do you delete a SQL view?
You use the “drop view” statement in SQL to delete an SQL view.
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The not-like operator in SQL can be used to find pattern matching.
44. What are the triggers before inserting them in SQL?
Insert triggers in SQL and modify or check record values before they are saved to the database. They allow access to values from the table for comparison purposes using the new and old keywords.
45. What is an auto-increment in SQL?
Auto increment is a feature in SQL that automatically generates and provides a unique value to every record in an SQL table.
This field is often used as the primary key column, where you must give an exceptional value for every requirement you add. It can also be used for unique constraint columns.
46. How can auto increment be started from another value in SQL?
Auto increment in SQL can be started using the alter table syntax from another value.
47. How can data definition commands be used in SQL?
Data definition commands include insert, use, create, alter, drop, update, and delete. For example, to correct a buddy’s salary, use “update employee” and “set” to change the salary value.
To drop a table, use “drop table” and specify the table’s name. After dropping the table, create a new table and insert the values.
48. What are the different types of standard forms in SQL?
There are three types of standard forms in SQL: the first normal form (1NF), the second standardform (2NF),and the third normal form (3NF).
49. What are the benefits of normalisation?
Normalisation promotes data integrity and provides data consistency, flexibility, higher security, and quicker execution.
50. What are regular expressions used for in SQL?
Regular expressions are used to filter out specific data in SQL. They help identify complex data sets and apply filters over numbers or special characters data.
51. What is the purpose of CTE in SQL?
CTE is a common table expression that uses a single select insert update or date statement to reference some or all the CTE columns. The syntax for a CTE is followed by a keyword and a name, such as highest salary.
52. What is MySQL Workbench?
MySQL Workbench is a tool for executing the top 5 free SQL queries. It interacts with MySQL, a relational database management system. The workbench consists of three modules: SQL development, data modelling, and server administration.
53. What is data modelling?
Data modelling involves designing a database schema using normalization or the entity-relationship diagram (ER diagram) method.
54. What are relationships between entities crucial in database management?
Relationships between entities are crucial in database management because they help to understand and manage the relationships between different entities within a database.
55. How can tables be created in SQL?
To create tables in SQL, select the complete section and press control shift to enter. The action output will show the creation of the table. Create tables for entities such as department, project, and dependent.
“Let’s now check out our MCQ’s section
1. In what year was MySQL introduced?
a) 2010
b) 2001
c) 1988
d)
2. What keyword is typically used to begin a SQL query for data retrieval?
a) Read
b) Get
c) Fetch
d)
3. Who developed SQL?
a) Microsoft
b) Google
c)
d) Apple
4. What elements does SQL contain as part of its database engine?
a)
b) Graphical interface, export tool, documentation
c) Web server, client application, caching mechanism
d) Execution planner, file manager, hardware interface
5. What types of data are SQL data types mainly classified into?
a) Excel, Word, Image, and Binary
b)
c) Audio, Video, String, and Object
d) Integer, Double, Char, and Array
6.Which types are SQL commands divided into?
a) HTTP, FTP, HTTPS, and SMTP
b) CREATE, MODIFY, STORE, and REMOVE
c)
d) IF, WHILE, FOR, and SWITCH
7. Which clause allows users to sort results in an SQL query?
a) GROUP BY clause
b) SELECT clause
c)
d) FROM clause
8. Which SQL operator compares two different data in SQL tables?
a) Assignment operators
b)
c) Logical operators
d) Concatenation operators
9. Which SQL commands include COMMIT and ROLLBACK?
a)
b) Data Definition Language (DDL)
c) Data Control Language (DCL)
d) Data Manipulation Language (DML)
10. What does the SQL JOIN operation do?
a) Align table headers to look uniform
b) Splits one table into multiple derived tables
c) Duplicates one table to create a backup copy
d)
Conclusion
As previously discussed, for data management to be successful it requires an in-depth knowledge of MySQL principles and functions as it’s one of the leading relational databases on the market today.
Our MySQL Questions Interview blog presents answers to frequently-asked MySQL Viva Questions about fundamental and advanced subjects. By learning these answers, you may demonstrate your competence and knowledge within this sector and be better equipped for any future interviews involving MySQL.
We truly hope this MySQL Interview Questions and Answers blog has been beneficial in your preparation process and wish you every success with all your future endeavours!
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