March 23, 2025

SQL MCQ Questions for Interviews and Exams Preparation

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sql mcq questions

SQL is the foundation of database management, making it essential for anyone working with structured data. Whether you’re preparing for exams, interviews, or just improving your skills, practicing SQL MCQ questions can enhance your understanding of queries, joins, indexing, and optimization techniques. These multiple-choice questions cover everything from basic SQL commands to complex database operations. By testing your knowledge with well-structured questions, you can identify weak areas and improve your problem-solving speed. This guide provides a set of SQL MCQs, covering different difficulty levels, along with expert tips to help you answer them correctly and boost your confidence.

Table of Contents

SQL MCQ Questions With Answers

sql mcq questions

1. What does SQL stand for?

  1. A) Structured Query Logic
  2. B) System Query Language
  3. C) Structured Query Language
  4. D) Sequential Query Logic
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Answer: C) Structured Query Language

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

  1. A) RETRIEVE
  2. B) FETCH
  3. C) SELECT
  4. D) GET

Answer: C) SELECT

3. Which command is used to remove all records from a table but keep the structure?

  1. A) DELETE
  2. B) DROP
  3. C) TRUNCATE
  4. D) REMOVE

Answer: C) TRUNCATE

4. What is the function of the WHERE clause?

  1. A) Sorts query results
  2. B) Groups records
  3. C) Filters records based on a condition
  4. D) Joins two tables

Answer: C) Filters records based on a condition

5. Which SQL statement is used to insert data into a table?

  1. A) INSERT INTO
  2. B) ADD RECORD
  3. C) PUT INTO
  4. D) UPDATE

Answer: A) INSERT INTO

6. Which SQL function is used to return the total number of rows in a table?

  1. A) COUNT()
  2. B) TOTAL()
  3. C) SUM()
  4. D) ROWS()

Answer: A) COUNT()

7. What is the default sorting order of the ORDER BY clause?

  1. A) Descending
  2. B) Random
  3. C) Ascending
  4. D) None

Answer: C) Ascending

8. What does the DISTINCT keyword do?

  1. A) Displays only duplicate values
  2. B) Retrieves unique records
  3. C) Removes NULL values
  4. D) Sorts records

Answer: B) Retrieves unique records

9. Which SQL keyword is used to sort results?

  1. A) SORT
  2. B) ARRANGE
  3. C) ORDER BY
  4. D) GROUP BY

Answer: C) ORDER BY

10. Which SQL constraint ensures that all column values are unique?

  1. A) UNIQUE
  2. B) PRIMARY KEY
  3. C) CHECK
  4. D) DEFAULT

Answer: A) UNIQUE

11. What is a primary key?

  1. A) A column that contains duplicate values
  2. B) A column that uniquely identifies each record
  3. C) A column used for sorting
  4. D) A column that allows NULL values

Answer: B) A column that uniquely identifies each record

12. Which of the following is a valid SQL JOIN type?

  1. A) INNER JOIN
  2. B) LEFT JOIN
  3. C) RIGHT JOIN
  4. D) All of the above

Answer: D) All of the above

13. What does the HAVING clause do?

  1. A) Filters grouped data
  2. B) Filters individual records
  3. C) Sorts query results
  4. D) Deletes duplicate records

Answer: A) Filters grouped data

14. Which SQL statement is used to modify existing data?

  1. A) MODIFY
  2. B) UPDATE
  3. C) CHANGE
  4. D) EDIT
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Answer: B) UPDATE

15. What is the difference between DELETE and TRUNCATE?

  1. A) DELETE removes data with conditions; TRUNCATE removes all records
  2. B) DELETE is faster than TRUNCATE
  3. C) TRUNCATE allows conditions; DELETE does not
  4. D) Both are identical

Answer: A) DELETE removes data with conditions; TRUNCATE removes all records

16. What is a foreign key?

  1. A) A key that is unique for every table
  2. B) A key linking two tables
  3. C) A key used for encryption
  4. D) A key that allows duplicate values

Answer: B) A key linking two tables

17. Which SQL command is used to remove a column from a table?

  1. A) DELETE COLUMN
  2. B) REMOVE COLUMN
  3. C) ALTER TABLE … DROP COLUMN
  4. D) CHANGE TABLE

Answer: C) ALTER TABLE … DROP COLUMN

18. What does the UNION operator do?

  1. A) Combines results of two queries and removes duplicates
  2. B) Merges two tables permanently
  3. C) Returns all duplicate records
  4. D) Deletes matching records

Answer: A) Combines results of two queries and removes duplicates

19. What is the purpose of indexing in SQL?

  1. A) Speeds up query performance
  2. B) Stores backup data
  3. C) Increases data size
  4. D) Prevents data modification

Answer: A) Speeds up query performance

20. What is the result of a LEFT JOIN if there is no match?

  1. A) NULL values in unmatched columns
  2. B) No records returned
  3. C) Only matching records displayed
  4. D) Error in query execution

Answer: A) NULL values in unmatched columns

21. What is normalization in SQL?

  1. A) The process of storing duplicate data
  2. B) Structuring databases to reduce redundancy
  3. C) Sorting data in tables
  4. D) Encrypting data

Answer: B) Structuring databases to reduce redundancy

22. What is the function of the AUTO_INCREMENT attribute?

  1. A) Automatically increases the column value
  2. B) Inserts random values
  3. C) Deletes duplicate records
  4. D) Prevents NULL values

Answer: A) Automatically increases the column value

23. How can you find duplicate records in a table?

  1. A) Using GROUP BY and HAVING COUNT()
  2. B) Using ORDER BY
  3. C) Using DISTINCT
  4. D) Using DELETE

Answer: A) Using GROUP BY and HAVING COUNT()

24. Which SQL command is used to grant privileges to a user?

  1. A) AUTHORIZE
  2. B) PERMIT
  3. C) GRANT
  4. D) ALLOW

Answer: C) GRANT

25. What is a stored procedure?

  1. A) A function stored in a database
  2. B) A predefined SQL query stored for reuse
  3. C) A temporary table
  4. D) A way to store passwords

Answer: B) A predefined SQL query stored for reuse

26. What is ACID in SQL transactions?

  1. A) A database optimization technique
  2. B) A set of properties ensuring reliable transactions
  3. C) A type of SQL query
  4. D) A security protocol

Answer: B) A set of properties ensuring reliable transactions

27. Which of the following is NOT an ACID property?

  1. A) Atomicity
  2. B) Consistency
  3. C) Durability
  4. D) Scalability

Answer: D) Scalability

28. What does the COMMIT command do?

  1. A) Ends a session
  2. B) Saves changes made in a transaction
  3. C) Rolls back changes
  4. D) Deletes all records in a table

Answer: B) Saves changes made in a transaction

29. Which command undoes changes made within a transaction?

  1. A) REVERT
  2. B) DELETE
  3. C) ROLLBACK
  4. D) REMOVE

Answer: C) ROLLBACK

30. What is a constraint in SQL?

  1. A) A rule applied to data columns
  2. B) A type of stored procedure
  3. C) A built-in function
  4. D) A query used for data retrieval

Answer: A) A rule applied to data columns

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31. Which SQL constraint is used to ensure a column cannot have NULL values?

  1. A) UNIQUE
  2. B) PRIMARY KEY
  3. C) NOT NULL
  4. D) DEFAULT

Answer: C) NOT NULL

32. Which SQL constraint automatically generates a unique value for each new row?

  1. A) PRIMARY KEY
  2. B) CHECK
  3. C) AUTO_INCREMENT
  4. D) DEFAULT

Answer: C) AUTO_INCREMENT

33. Which SQL clause is used to limit the number of records returned in a query?

  1. A) FILTER
  2. B) LIMIT
  3. C) MAX
  4. D) RESTRICT

Answer: B) LIMIT

34. What is the main purpose of indexing in SQL?

  1. A) To store duplicate data
  2. B) To improve query performance
  3. C) To add security to databases
  4. D) To allow foreign keys

Answer: B) To improve query performance

35. What is an execution plan in SQL?

  1. A) A method to run queries faster
  2. B) A strategy for query execution chosen by the SQL engine
  3. C) A table structure
  4. D) A feature for database backups

Answer: B) A strategy for query execution chosen by the SQL engine

36. What does the ANALYZE command do in SQL?

  1. A) Finds duplicate records
  2. B) Optimizes the execution plan
  3. C) Removes NULL values
  4. D) Deletes records

Answer: B) Optimizes the execution plan

37. What is a view in SQL?

  1. A) A temporary table storing query results
  2. B) A virtual table based on an SQL query
  3. C) A feature to optimize databases
  4. D) A reserved keyword

Answer: B) A virtual table based on an SQL query

38. Can a SQL view contain multiple tables?

  1. A) Yes
  2. B) No

Answer: A) Yes

39. Which type of JOIN returns only matching records from both tables?

  1. A) INNER JOIN
  2. B) LEFT JOIN
  3. C) RIGHT JOIN
  4. D) FULL JOIN

Answer: A) INNER JOIN

40. What is a correlated subquery?

  1. A) A subquery that executes separately
  2. B) A subquery that depends on the main query for execution
  3. C) A query that combines multiple results
  4. D) A query used for indexing

Answer: B) A subquery that depends on the main query for execution

41. Which SQL command is used to grant permissions to a user?

  1. A) ALLOW
  2. B) AUTHORIZE
  3. C) GRANT
  4. D) PERMIT

Answer: C) GRANT

42. Which command is used to remove user access rights?

  1. A) REVOKE
  2. B) REMOVE
  3. C) DELETE USER
  4. D) DENY

Answer: A) REVOKE

43. What does SQL injection exploit?

  1. A) Weak authentication
  2. B) Poorly validated user input
  3. C) Slow query execution
  4. D) Outdated database versions

Answer: B) Poorly validated user input

44. What is the main difference between SQL and NoSQL databases?

  1. A) SQL uses structured data, NoSQL supports unstructured data
  2. B) NoSQL is only for large databases
  3. C) SQL is used for images, NoSQL is used for text
  4. D) NoSQL cannot support transactions

Answer: A) SQL uses structured data, NoSQL supports unstructured data

45. What is a self-join in SQL?

  1. A) A join that references the same table
  2. B) A join between unrelated tables
  3. C) A join between different databases
  4. D) A feature for backup storage

Answer: A) A join that references the same table

46. What is the function of the CASE statement in SQL?

  1. A) Allows conditional logic in queries
  2. B) Sorts records in descending order
  3. C) Stores encrypted data
  4. D) Deletes duplicate records

Answer: A) Allows conditional logic in queries

47. What is the default isolation level in most relational databases?

  1. A) READ UNCOMMITTED
  2. B) READ COMMITTED
  3. C) SERIALIZABLE
  4. D) REPEATABLE READ

Answer: B) READ COMMITTED

48. Which SQL function returns the first non-null value from a list?

  1. A) COALESCE
  2. B) NULLIF
  3. C) ISNULL
  4. D) IFNULL

Answer: A) COALESCE

49. How does partitioning improve query performance?

  1. A) By splitting tables into smaller, manageable sections
  2. B) By compressing the data
  3. C) By storing queries for reuse
  4. D) By removing duplicates

Answer: A) By splitting tables into smaller, manageable sections

50. What does the CTE (Common Table Expression) do?

  1. A) Creates a temporary result set for reuse in queries
  2. B) Deletes duplicate rows
  3. C) Prevents SQL injection
  4. D) Optimizes indexing

Answer: A) Creates a temporary result set for reuse in queries

51. Which SQL statement creates an index?

  1. A) MAKE INDEX
  2. B) ADD INDEX
  3. C) CREATE INDEX
  4. D) BUILD INDEX

Answer: C) CREATE INDEX

52. What does the DROP command do?

  1. A) Removes all records from a table
  2. B) Deletes the entire table structure
  3. C) Removes duplicate records
  4. D) Deactivates table constraints

Answer: B) Deletes the entire table structure

53. What does the EXISTS operator check?

  1. A) If a table has NULL values
  2. B) If a subquery returns any records
  3. C) If a column has unique values
  4. D) If a function is properly defined

Answer: B) If a subquery returns any records

54. What is the purpose of the DEFAULT constraint in SQL?

  1. A) Ensures that a column cannot have NULL values
  2. B) Assigns a default value if no value is provided
  3. C) Creates an index automatically
  4. D) Defines the data type of a column

Answer: B) Assigns a default value if no value is provided

55. Which of the following commands is used to rename an existing table?

  1. A) RENAME TABLE
  2. B) ALTER TABLE … RENAME TO
  3. C) UPDATE TABLE
  4. D) MODIFY TABLE

Answer: B) ALTER TABLE … RENAME TO

56. Which SQL function is used to get the current date?

  1. A) CURRENT_DATE()
  2. B) NOW()
  3. C) GET_DATE()
  4. D) DATE()

Answer: A) CURRENT_DATE()

57. What will happen if you try to insert a NULL value into a NOT NULL column?

  1. A) The record will be inserted successfully
  2. B) SQL will replace NULL with a default value
  3. C) An error will occur
  4. D) The NULL value will be stored as empty

Answer: C) An error will occur

58. Which SQL keyword is used to remove duplicate records from a result set?

  1. A) UNIQUE
  2. B) DISTINCT
  3. C) FILTER
  4. D) GROUP BY

Answer: B) DISTINCT

59. What is the main purpose of the ALTER TABLE command?

  1. A) Delete records from a table
  2. B) Modify the structure of an existing table
  3. C) Retrieve data from a table
  4. D) Sort data in a table

Answer: B) Modify the structure of an existing table

60. What is the purpose of the LIMIT clause in SQL?

  1. A) Restricts the number of rows returned in a query
  2. B) Sorts data in descending order
  3. C) Filters results based on conditions
  4. D) Combines multiple queries

Answer: A) Restricts the number of rows returned in a query

Wrapping Up

Practicing SQL MCQ questions is one of the best ways to improve your understanding of database concepts and boost your problem-solving speed. These questions help reinforce key topics such as joins, indexing, constraints, and transactions while preparing you for exams and technical interviews. By regularly testing your knowledge, you can identify areas that need improvement and build confidence in handling real-world SQL challenges. Whether you’re a beginner or an experienced professional, consistent practice with SQL MCQs will strengthen your skills and improve your query-writing efficiency, ultimately helping you succeed in both academic and professional settings. Keep practicing and growing!

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