SQL Quiz Test Online (30 random Questions) 2025

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 clause is used to set a condition on aggregated data?

A) WHERE

B) HAVING

C) GROUP BY

D) FILTER

2 / 30

2. What is a security patch in database systems?

A) A tool to optimize queries

B) A fix for identified vulnerabilities

C) A backup of the database

D) A new feature added to the database

3 / 30

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

A) A method for locking tables

B) A schema for normalization

C) A record of all database queries

D) A record of all changes made to the database

4 / 30

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

A) OUTER JOIN

B) INNER JOIN

C) FULL JOIN

D) CROSS JOIN

5 / 30

5. What does SQL stand for?

A) Simple Query Language

B) Sequential Query Language

C) Standard Query Language

D) Structured Query Language

6 / 30

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

A) A reference to a primary key in another table

B) A default value for columns

C) A unique identifier for each record

D) A key that cannot be used

7 / 30

7. Which SQL command removes a table from the database?

A) REMOVE

B) DELETE

C) TRUNCATE

D) DROP

8 / 30

8. Which operator is used to combine the results of two queries?

A) MERGE

B) CONNECT

C) JOIN

D) UNION

9 / 30

9. What is a database index?

A) None of the above

B) A duplicate of a table

C) A pointer to data in a table

D) A key for foreign table linking

10 / 30

10. What type of dependency does 3NF eliminate?

A) Partial dependency

B) Circular dependency

C) Transitive dependency

D) Multivalued dependency

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11. What is a composite key?

A) A single unique key

B) None of the above

C) A combination of two or more columns as a key

D) A duplicate key

12 / 30

12. How do you check if a column contains NULL values?

A) = NULL

B) CHECK NULL

C) IS NULL

D) HAS NULL

13 / 30

13. What is a foreign key?

A) A backup key

B) None of the above

C) A unique identifier for a table

D) A key linking two tables

14 / 30

14. In database design, what does 'schema' refer to?

A) A graphical representation of data

B) A database backup method

C) The structure of a database, including tables and relationships

D) A query optimization technique

15 / 30

15. What is SQL injection?

A) A way to encrypt database records

B) A method of creating backups

C) A database optimization technique

D) A security vulnerability allowing malicious SQL code execution

16 / 30

16. Which statement about stored procedures is true?

A) They cannot accept input parameters

B) They are automatically optimized for performance by the database

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

D) They are executed automatically on database startup

17 / 30

17. Which SQL keyword is used to sort the result set?

A) GROUP BY

B) SORT

C) FILTER

D) ORDER BY

18 / 30

18. What does ER stand for in ER Diagram?

A) Entity Relationship

B) Event Reaction

C) External Resource

D) Entity Reference

19 / 30

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

A) To execute SQL queries

B) To define the structure of the database

C) To grant user permissions

D) To store backup files

20 / 30

20. What is the role of a public key in asymmetric encryption?

A) To create indexes

B) To store database logs

C) To encrypt data

D) To decrypt data

21 / 30

21. What is a primary key?

A) A duplicate identifier for a table record

B) A command to fetch records

C) None of the above

D) A unique identifier for a table record

22 / 30

22. How does a CROSS JOIN behave?

A) Joins rows with matching primary keys

B) Joins rows with null values

C) Matches rows from two tables based on a condition

D) Produces a Cartesian product of two tables

23 / 30

23. Which of the following best describes a self-join?

A) A join between two different tables

B) A join that merges columns

C) A join that excludes null values

D) A join of a table with itself

24 / 30

24. What is the maximum number of primary keys a table can have?

A) None

B) 2

C) 1

D) Unlimited

25 / 30

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

A) Symmetric uses one key; asymmetric uses two keys

B) There is no difference

C) Asymmetric is faster than symmetric

D) Symmetric encrypts only text; asymmetric encrypts all data

26 / 30

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

A) BLOCK TABLE

B) LOCK TABLE

C) FREEZE TABLE

D) SECURE TABLE

27 / 30

27. What is the primary focus of the 5th Normal Form (5NF)?

A) Ensuring atomic columns

B) Removing join dependencies

C) Eliminating partial dependencies

D) Eliminating composite keys

28 / 30

28. What does the GROUP BY clause do?

A) Sorts rows

B) Filters rows

C) Deletes duplicate rows

D) Groups rows with the same values

29 / 30

29. What is the main drawback of normalization?

A) Increases redundancy

B) Reduces database size

C) Reduces data integrity

D) Slower write operations due to more joins

30 / 30

30. Which aggregate function calculates the sum of a column?

A) SUM()

B) MAX()

C) AVG()

D) COUNT()

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