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 happens if a table is not normalized?

A) Increased redundancy and anomalies

B) Elimination of relationships

C) Reduced storage usage

D) Improved performance

2 / 30

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

A) To execute SQL queries

B) To store backup files

C) To grant user permissions

D) To define the structure of the database

3 / 30

3. What is a scalar subquery?

A) A subquery that returns a single value

B) A subquery used in joins

C) A subquery that returns multiple rows

D) A subquery that updates data

4 / 30

4. Which function returns the current date in SQL?

A) NOW()

B) All of the above

C) CURDATE()

D) GETDATE()

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5. What does the JOIN clause do in SQL?

A) Combines data from multiple tables

B) Creates a new table

C) Updates records

D) Deletes records

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6. What is a foreign key?

A) A key linking two tables

B) A backup key

C) None of the above

D) A unique identifier for a table

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7. What is a composite key?

A) A duplicate key

B) None of the above

C) A single unique key

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

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8. How do you combine data from multiple tables?

A) JOIN

B) GROUP BY

C) UNION

D) CONNECT

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9. How do you retrieve unique values from a column?

A) GROUP BY

B) UNIQUE

C) DISTINCT

D) FILTER

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

A) WHERE

B) HAVING

C) FILTER

D) GROUP BY

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

A) JOIN

B) MERGE

C) UNION

D) CONNECT

12 / 30

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

A) SECURE TABLE

B) FREEZE TABLE

C) LOCK TABLE

D) BLOCK TABLE

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

A) Returns the next value in a set

B) Returns the previous value in a set

C) Computes a running total

D) Returns the average value of a set

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14. What is the purpose of an index in SQL?

A) To store duplicate data

B) To sort data

C) To ensure data integrity

D) To speed up data retrieval

15 / 30

15. What is the purpose of using roles in database security?

A) To encrypt sensitive data

B) To group permissions for easier management

C) To optimize query performance

D) To create backup strategies

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16. What is the default sorting order in SQL?

A) Descending

B) Random

C) Ascending

D) None

17 / 30

17. Which SQL function can identify the current user?

A) CURRENT_USER()

B) USER()

C) SESSION_USER()

D) All of the above

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

A) A record of all changes made to the database

B) A method for locking tables

C) A record of all database queries

D) A schema for normalization

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19. Which command is used to remove duplicate rows in a query result?

A) FILTER

B) UNIQUE

C) GROUP BY

D) DISTINCT

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20. Which command is used to create a new table in a database?

A) ADD TABLE

B) NEW TABLE

C) CREATE TABLE

D) INSERT

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21. What is a window function in SQL?

A) A function that operates on a subset of rows

B) A function that partitions data for analysis

C) All of the above

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

22 / 30

22. What is the purpose of the UPDATE command?

A) Modify existing records

B) Delete records

C) Insert new records

D) Create tables

23 / 30

23. Why are foreign keys important in database design?

A) They act as composite keys

B) They reduce redundancy

C) They improve query performance

D) They enforce referential integrity

24 / 30

24. What is the first step in database normalization?

A) Removing foreign keys

B) Adding composite keys

C) Eliminating redundant data

D) Ensuring all columns are atomic

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

A) Eliminating partial dependencies

B) Eliminating composite keys

C) Ensuring atomic columns

D) Removing join dependencies

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26. In a database table, what does 'redundancy' mean?

A) Efficient indexing

B) Data integrity

C) Optimal storage utilization

D) Duplicate or repetitive data

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27. What is normalization in databases?

A) Simplifying queries

B) Adding redundancy

C) Increasing database size

D) Removing redundant data

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28. What is the difference between DELETE and TRUNCATE?

A) DELETE resets indexes; TRUNCATE does not

B) DELETE removes specific rows; TRUNCATE removes all rows

C) DELETE is faster than TRUNCATE

D) DELETE removes all rows; TRUNCATE removes specific rows

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

A) Issues caused by redundant data

B) Normal data storage

C) Data security breaches

D) Enhanced query speed

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30. How does database mirroring enhance security?

A) By auditing user activities

B) By replicating data to a standby server

C) By preventing SQL injection

D) By encrypting data

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