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.

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

A) Data integrity

B) Efficient indexing

C) Optimal storage utilization

D) Duplicate or repetitive data

2 / 30

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

A) GROUP BY

B) UNIQUE

C) FILTER

D) DISTINCT

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3. How does database mirroring enhance security?

A) By preventing SQL injection

B) By auditing user activities

C) By replicating data to a standby server

D) By encrypting data

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4. What is a subquery?

A) A type of join

B) None of the above

C) A temporary table

D) A query within another query

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5. What is a database index?

A) A duplicate of a table

B) A pointer to data in a table

C) A key for foreign table linking

D) None of the above

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6. 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) Computes a running total

D) Returns the previous value in a set

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

A) 4NF

B) 3NF

C) BCNF

D) 5NF

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8. What is a window function in SQL?

A) All of the above

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

C) A function that operates on a subset of rows

D) A function that partitions data for analysis

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9. What does the DISTINCT keyword do?

A) Selects unique records

B) Deletes duplicate records

C) Filters records

D) Sorts records

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

A) LIKE

B) PATTERN

C) SEARCH

D) MATCH

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

A) WHERE

B) HAVING

C) GROUP BY

D) ORDER BY

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12. Which of the following is a type of SQL statement?

A) All of the above

B) Data Definition Language (DDL)

C) Data Manipulation Language (DML)

D) Data Control Language (DCL)

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13. What is a primary key?

A) A command to fetch records

B) A unique identifier for a table record

C) None of the above

D) A duplicate identifier for a table record

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14. How does a CROSS JOIN behave?

A) Joins rows with matching primary keys

B) Matches rows from two tables based on a condition

C) Joins rows with null values

D) Produces a Cartesian product of two tables

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

A) ALTER

B) INSERT

C) UPDATE

D) ADD

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

A) Using two databases for authentication

B) Authenticating two users simultaneously

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

D) Using two levels of encryption

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17. What is the purpose of the UNION operator?

A) Deletes records

B) Filters duplicate rows

C) Joins tables

D) Combines results of two queries

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18. How can database performance be monitored?

A) Tracking server resource usage

B) All of the above

C) Analyzing query execution plans

D) Using performance monitoring tools

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

A) To store database logs

B) To decrypt data

C) To create indexes

D) To encrypt data

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20. What is the purpose of database auditing?

A) To optimize query performance

B) To track and log database activities

C) To design database schemas

D) To encrypt database files

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21. What does the IN operator do?

A) Deletes rows

B) Matches a value within a set

C) Sorts rows

D) Filters rows

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

A) A key that cannot be used

B) A default value for columns

C) A reference to a primary key in another table

D) A unique identifier for each record

23 / 30

23. What type of dependency does 3NF eliminate?

A) Multivalued dependency

B) Transitive dependency

C) Circular dependency

D) Partial dependency

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

A) ROWCOUNT()

B) SUM()

C) COUNT()

D) TOTAL()

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25. Which command is used to modify existing rows in a table?

A) UPDATE

B) ALTER

C) MODIFY

D) INSERT

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

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

B) Combines rows with matching values only

C) Joins rows with null values only

D) Joins rows based on primary keys

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27. How does the SQL MERGE statement work?

A) Merges two tables into one new table

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

C) Combines columns from two queries into one result set

D) Optimizes indexes for faster retrieval

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

A) Ensuring atomic columns

B) Removing join dependencies

C) Eliminating composite keys

D) Eliminating partial dependencies

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

A) DELETE

B) REMOVE

C) DROP

D) TRUNCATE

30 / 30

30. What does the GROUP BY clause do?

A) Groups rows with the same values

B) Filters rows

C) Sorts rows

D) Deletes duplicate rows

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