SQL Quiz Test Online (30 random Questions) 2026

This quick 30-minute challenge consists of 30 random multiple-choice questions designed to test your knowledge across various SQL topics, including the introduction to databases, data manipulation and querying, database design and normalization, advanced SQL concepts, and database administration and security. Whether you’re a beginner or looking to expand your SQL expertise, this quiz will enhance your understanding of database management and querying skills.

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30 Minutes SQL Quiz Test Online

Welcome to the SQL Quiz! This quick 30-minute challenge consists of 30 random multiple-choice questions designed to test your knowledge across various SQL topics, including the introduction to databases, data manipulation and querying, database design and normalization, advanced SQL concepts, and database administration and security. Whether you're a beginner or looking to expand your SQL expertise, this quiz will enhance your understanding of database management and querying skills.

1 / 30

1. Which SQL keyword is used to combine results from multiple queries?

A) JOIN

B) EXCEPT

C) UNION

D) INTERSECT

2 / 30

2. How do you remove a specific record from a table?

A) DELETE

B) DROP

C) REMOVE

D) TRUNCATE

3 / 30

3. What is the primary purpose of a database schema?

A) To define the structure of the database

B) To store backup files

C) To grant user permissions

D) To execute SQL queries

4 / 30

4. What is SQL injection?

A) A database optimization technique

B) A way to encrypt database records

C) A security vulnerability allowing malicious SQL code execution

D) A method of creating backups

5 / 30

5. How do you add a new column to an existing table?

A) INSERT COLUMN

B) ALTER TABLE

C) UPDATE TABLE

D) ADD COLUMN

6 / 30

6. What is a 'transaction log' in database management?

A) A record of all database queries

B) A method for locking tables

C) A record of all changes made to the database

D) A schema for normalization

7 / 30

7. Which command is used to remove a user in SQL?

A) DROP USER

B) ALTER USER

C) DELETE USER

D) REMOVE USER

8 / 30

8. How does the SQL MERGE statement work?

A) Merges two tables into one new table

B) Optimizes indexes for faster retrieval

C) Performs insert, update, or delete operations based on a condition

D) Combines columns from two queries into one result set

9 / 30

9. What does a foreign key represent in a database?

A) A reference to a primary key in another table

B) A key that cannot be used

C) A unique identifier for each record

D) A default value for columns

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10. How does the LAG() function work in SQL?

A) Computes a running total

B) Returns the previous value in a set

C) Returns the average value of a set

D) Returns the next value in a set

11 / 30

11. What is functional dependency in a database?

A) A relationship between two columns

B) A relationship between two tables

C) A function that manages data

D) A dependency between primary keys

12 / 30

12. Which of the following is not a type of SQL join?

A) FULL JOIN

B) OUTER JOIN

C) INNER JOIN

D) CROSS JOIN

13 / 30

13. What does the term 'two-factor authentication' (2FA) mean?

A) Verifying identity with two methods (e.g., password and OTP)

B) Using two databases for authentication

C) Using two levels of encryption

D) Authenticating two users simultaneously

14 / 30

14. What does the GROUP BY clause do?

A) Sorts rows

B) Deletes duplicate rows

C) Groups rows with the same values

D) Filters rows

15 / 30

15. Which SQL command is used to grant permissions to a user?

A) ALLOW

B) PERMIT

C) GRANT

D) ASSIGN

16 / 30

16. Which clause is used to filter rows in a SELECT query?

A) HAVING

B) GROUP BY

C) FILTER

D) WHERE

17 / 30

17. What is the main difference between a UNION and a UNION ALL?

A) UNION ALL removes duplicates; UNION does not

B) UNION is faster than UNION ALL

C) UNION removes duplicates; UNION ALL does not

D) UNION merges columns; UNION ALL merges rows

18 / 30

18. What does the JOIN clause do in SQL?

A) Deletes records

B) Combines data from multiple tables

C) Updates records

D) Creates a new table

19 / 30

19. Which SQL function can identify the current user?

A) CURRENT_USER()

B) All of the above

C) SESSION_USER()

D) USER()

20 / 30

20. What is the primary role of a database administrator (DBA)?

A) Managing and securing the database system

B) Writing application code

C) Developing mobile applications

D) Designing user interfaces

21 / 30

21. How do you rename a column in the result set?

A) RENAME

B) ALIAS

C) USING

D) AS

22 / 30

22. What is denormalization?

A) Combining tables to improve performance

B) Normalizing a database to BCNF

C) Eliminating all keys from a table

D) Breaking tables into smaller parts

23 / 30

23. What is the result of a CROSS JOIN?

A) Cartesian product of two tables

B) Difference of two tables

C) Union of two tables

D) Intersection of two tables

24 / 30

24. What is the purpose of the ROW_NUMBER() function?

A) Creates a unique index

B) Assigns unique numbers to rows within a partition

C) Calculates the total number of rows in a table

D) Assigns ranks with gaps for duplicates

25 / 30

25. Which SQL command is used to retrieve data from a database?

A) INSERT

B) SELECT

C) DELETE

D) UPDATE

26 / 30

26. What is the purpose of a Common Table Expression (CTE)?

A) To simplify complex queries by defining a temporary result set

B) To optimize indexing

C) To create temporary tables

D) To perform transactions

27 / 30

27. What is the primary use of a FULL OUTER JOIN?

A) Joins rows based on primary keys

B) Combines rows with matching values only

C) Includes all rows from both tables, matching where possible

D) Joins rows with null values only

28 / 30

28. What happens if a table is not normalized?

A) Improved performance

B) Increased redundancy and anomalies

C) Reduced storage usage

D) Elimination of relationships

29 / 30

29. What does the IN operator do?

A) Deletes rows

B) Sorts rows

C) Matches a value within a set

D) Filters rows

30 / 30

30. What is the default sorting order in SQL?

A) None

B) Ascending

C) Random

D) Descending

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