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 is the primary purpose of a database schema?

A) To define the structure of the database

B) To execute SQL queries

C) To store backup files

D) To grant user permissions

2 / 30

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

A) UPDATE TABLE

B) ALTER TABLE

C) ADD COLUMN

D) INSERT COLUMN

3 / 30

3. 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

4 / 30

4. Which normal form eliminates partial dependency?

A) 3NF

B) BCNF

C) 2NF

D) 1NF

5 / 30

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

A) ORDER BY

B) DISTINCT

C) GROUP BY

D) UNION

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

A) Eliminating composite keys

B) Removing join dependencies

C) Eliminating partial dependencies

D) Ensuring atomic columns

7 / 30

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

A) Assigns ranks with gaps for duplicates

B) Assigns unique numbers to rows within a partition

C) Creates a unique index

D) Calculates the total number of rows in a table

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8. How can unauthorized database access be prevented?

A) By implementing firewalls

B) All of the above

C) By enforcing strong authentication methods

D) By regularly updating security patches

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

A) HAS NULL

B) CHECK NULL

C) = NULL

D) IS NULL

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10. What is a scalar subquery?

A) A subquery that updates data

B) A subquery that returns a single value

C) A subquery that returns multiple rows

D) A subquery used in joins

11 / 30

11. Which command is used to add new rows to a table?

A) ADD

B) INSERT

C) ALTER

D) UPDATE

12 / 30

12. What is the first step in database normalization?

A) Ensuring all columns are atomic

B) Eliminating redundant data

C) Adding composite keys

D) Removing foreign keys

13 / 30

13. Which normal form is achieved when every determinant is a candidate key?

A) BCNF

B) 3NF

C) 4NF

D) 5NF

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14. What does the term 'role-based access control' (RBAC) mean?

A) Granting access based on predefined roles

B) Assigning permissions to individual users

C) Backing up the database

D) Encrypting sensitive data

15 / 30

15. What is a primary key?

A) A unique identifier for a table record

B) A command to fetch records

C) A duplicate identifier for a table record

D) None of the above

16 / 30

16. How does the SQL MERGE statement work?

A) Combines columns from two queries into one result set

B) Optimizes indexes for faster retrieval

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

D) Merges two tables into one new table

17 / 30

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

A) INSERT

B) DELETE

C) SELECT

D) UPDATE

18 / 30

18. Which keyword is used to match patterns in SQL?

A) LIKE

B) PATTERN

C) MATCH

D) SEARCH

19 / 30

19. Which method helps protect against SQL injection?

A) Using stored procedures

B) Parameterized queries

C) All of the above

D) Input validation

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20. How do you find the highest value in a column?

A) MIN()

B) MAX()

C) TOP()

D) HIGHEST()

21 / 30

21. How does database mirroring enhance security?

A) By replicating data to a standby server

B) By auditing user activities

C) By encrypting data

D) By preventing SQL injection

22 / 30

22. 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

23 / 30

23. What does the IN operator do?

A) Deletes rows

B) Sorts rows

C) Matches a value within a set

D) Filters rows

24 / 30

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

A) COUNT()

B) ROWCOUNT()

C) TOTAL()

D) SUM()

25 / 30

25. How do you combine data from multiple tables?

A) UNION

B) GROUP BY

C) JOIN

D) CONNECT

26 / 30

26. What does BCNF stand for?

A) Basic Composite Normal Form

B) Boyce-Codd Normal Form

C) None of the above

D) Binary Conjugate Normal Form

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27. What happens if a table is not normalized?

A) Elimination of relationships

B) Reduced storage usage

C) Improved performance

D) Increased redundancy and anomalies

28 / 30

28. What is the purpose of the UPDATE command?

A) Modify existing records

B) Create tables

C) Insert new records

D) Delete records

29 / 30

29. What is the key benefit of schema normalization in large databases?

A) Simplifies data visualization

B) Ensures better data visualization

C) Reduces storage requirements and improves data consistency

D) Eliminates indexing needs

30 / 30

30. What does the REVOKE command do?

A) Denies access to the database

B) Deletes user accounts

C) Creates a backup of permissions

D) Removes permissions from a user

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