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. What does the GROUP BY clause do?

A) Groups rows with the same values

B) Filters rows

C) Deletes duplicate rows

D) Sorts rows

2 / 30

2. What is the difference between DELETE and TRUNCATE?

A) DELETE resets indexes; TRUNCATE does not

B) DELETE removes all rows; TRUNCATE removes specific rows

C) DELETE is faster than TRUNCATE

D) DELETE removes specific rows; TRUNCATE removes all rows

3 / 30

3. What does ER stand for in ER Diagram?

A) Event Reaction

B) Entity Reference

C) External Resource

D) Entity Relationship

4 / 30

4. What is a composite key?

A) A primary key consisting of multiple columns

B) A foreign key with a single column

C) A key used for indexing

D) A temporary key

5 / 30

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

A) Designing user interfaces

B) Writing application code

C) Managing and securing the database system

D) Developing mobile applications

6 / 30

6. Which SQL function can identify the current user?

A) USER()

B) SESSION_USER()

C) CURRENT_USER()

D) All of the above

7 / 30

7. Why are foreign keys important in database design?

A) They reduce redundancy

B) They enforce referential integrity

C) They act as composite keys

D) They improve query performance

8 / 30

8. What does the HAVING clause do?

A) None of the above

B) Filters grouped data

C) Deletes grouped data

D) Joins tables

9 / 30

9. Which clause is used to combine rows with the same values?

A) DISTINCT

B) GROUP BY

C) ORDER BY

D) UNION

10 / 30

10. What does the term 'data anomaly' mean?

A) Normal data storage

B) Issues caused by redundant data

C) Enhanced query speed

D) Data security breaches

11 / 30

11. 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 perform transactions

D) To create temporary tables

12 / 30

12. Which command is used to delete all rows from a table without removing the table?

A) TRUNCATE

B) DELETE

C) REMOVE

D) DROP

13 / 30

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

A) Calculates the total number of rows in a table

B) Creates a unique index

C) Assigns ranks with gaps for duplicates

D) Assigns unique numbers to rows within a partition

14 / 30

14. Which SQL function is used to count the number of rows in a table?

A) COUNT()

B) SUM()

C) ROWCOUNT()

D) TOTAL()

15 / 30

15. What is functional dependency in a database?

A) A dependency between primary keys

B) A relationship between two columns

C) A function that manages data

D) A relationship between two tables

16 / 30

16. What does 'principle of least privilege' mean in database security?

A) Assigning minimum access necessary for users

B) Encrypting sensitive data

C) Allowing all users full database access

D) Removing unused tables and columns

17 / 30

17. What is a disaster recovery plan in database management?

A) A guide to install database software

B) A strategy to recover data in case of failure

C) A method to grant user permissions

D) A plan to optimize database queries

18 / 30

18. How is sensitive data protected in a database?

A) By limiting user access

B) All of the above

C) By auditing and monitoring activities

D) By using encryption

19 / 30

19. What is the difference between symmetric and asymmetric encryption in databases?

A) Asymmetric is faster than symmetric

B) Symmetric uses one key; asymmetric uses two keys

C) There is no difference

D) Symmetric encrypts only text; asymmetric encrypts all data

20 / 30

20. What is a window function in SQL?

A) A function that performs calculations across a window of rows

B) All of the above

C) A function that partitions data for analysis

D) A function that operates on a subset of rows

21 / 30

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

A) Returns the average value of a set

B) Returns the next value in a set

C) Returns the previous value in a set

D) Computes a running total

22 / 30

22. Which normal form eliminates partial dependency?

A) BCNF

B) 1NF

C) 2NF

D) 3NF

23 / 30

23. What does the LIKE operator do?

A) Sorts data

B) Deletes records

C) Matches a pattern in a string

D) Joins tables

24 / 30

24. What does the NVL() function do in SQL?

A) Converts a null value to a specified value

B) Calculates the sum of a column

C) Removes duplicate rows from a query

D) Joins two tables based on a condition

25 / 30

25. Which command is used to lock a table in SQL?

A) LOCK TABLE

B) SECURE TABLE

C) FREEZE TABLE

D) BLOCK TABLE

26 / 30

26. Which statement about stored procedures is true?

A) They cannot accept input parameters

B) They are executed automatically on database startup

C) They are automatically optimized for performance by the database

D) They can be used to encapsulate complex SQL queries and business logic

27 / 30

27. What is the purpose of the UPDATE command?

A) Modify existing records

B) Create tables

C) Insert new records

D) Delete records

28 / 30

28. How can user activity be restricted during maintenance?

A) By revoking all permissions

B) By shutting down the database

C) By switching to read-only mode

D) By locking the database

29 / 30

29. How does PARTITION BY enhance window functions?

A) Joins rows with matching values

B) Eliminates null values

C) Divides data into subsets for analysis

D) Aggregates data within a table

30 / 30

30. Which SQL clause is used to filter grouped data?

A) GROUP BY

B) ORDER BY

C) HAVING

D) WHERE

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