20 MySQL Quiz Questions and Answers

Question 1:
What is the primary function of the MySQL command “SELECT * FROM table_name;”?
A. To insert new records into the table
B. To retrieve all records from the table
C. To delete the table
D. To update existing records in the table
Correct Answer: B
Explanation: The SELECT statement is used to query data from a table, and “*” means all columns, so it retrieves all records from the specified table.

Question 2:
Which data type in MySQL is used for storing variable-length strings?
A. INT
B. VARCHAR
C. DATE
D. FLOAT
Correct Answer: B
Explanation: VARCHAR is designed for variable-length strings, allowing storage of up to a specified length while optimizing space.

Question 3:
What does the MySQL command “DROP TABLE table_name;” do?
A. Renames the table
B. Deletes the table and its data permanently
C. Adds a new column to the table
D. Creates a backup of the table
Correct Answer: B
Explanation: The DROP TABLE command removes the table structure and all associated data from the database.

Question 4:
In MySQL, which keyword is used to add a unique constraint to a column?
A. PRIMARY KEY
B. FOREIGN KEY
C. UNIQUE
D. INDEX
Correct Answer: C
Explanation: The UNIQUE keyword ensures that all values in a column are distinct, preventing duplicate entries.

Question 5:
What is the purpose of the MySQL function NOW()?
A. To get the current date and time
B. To format a date string
C. To calculate the difference between two dates
D. To convert a string to a date
Correct Answer: A
Explanation: The NOW() function returns the current date and time from the system where the MySQL server is running.

Question 6:
Which MySQL statement is used to modify existing records in a table?
A. INSERT INTO
B. DELETE FROM
C. UPDATE
D. SELECT
Correct Answer: C
Explanation: The UPDATE statement is specifically used to modify the data in existing rows of a table based on specified conditions.

Question 7:
What does the INNER JOIN clause do in a MySQL query?
A. Returns all records from both tables
B. Returns only the records with matching values in both tables
C. Returns all records from the left table
D. Returns all records from the right table
Correct Answer: B
Explanation: INNER JOIN combines rows from two or more tables based on a related column, returning only the matching rows.

Question 8:
In MySQL, how do you specify a column as auto-incrementing?
A. AUTO_INCREMENT keyword
B. INCREMENT keyword
C. AUTO KEY
D. SEQUENCE
Correct Answer: A
Explanation: The AUTO_INCREMENT attribute is added to a column definition to automatically generate a unique number for new records.

Question 9:
What is the MySQL command to start a transaction?
A. COMMIT
B. ROLLBACK
C. BEGIN or START TRANSACTION
D. END TRANSACTION
Correct Answer: C
Explanation: BEGIN or START TRANSACTION initiates a transaction block, allowing multiple operations to be treated as a single unit.

Question 10:
Which MySQL storage engine supports full-text searching?
A. MyISAM
B. InnoDB
C. MEMORY
D. Both A and B
Correct Answer: D
Explanation: Both MyISAM and InnoDB storage engines support full-text searching, though InnoDB is more commonly used for its features.

Question 11:
What does the GROUP BY clause in a MySQL SELECT statement do?
A. Sorts the results in ascending order
B. Aggregates data based on one or more columns
C. Filters rows based on conditions
D. Joins multiple tables
Correct Answer: B
Explanation: GROUP BY groups rows that have the same values in specified columns and is often used with aggregate functions like COUNT or SUM.

Question 12:
In MySQL, what is the default port number for the server?
A. 3306
B. 8080
C. 1433
D. 1521
Correct Answer: A
Explanation: MySQL server listens on port 3306 by default for incoming connections.

Question 13:
Which MySQL command is used to create an index on a table?
A. CREATE INDEX
B. MAKE INDEX
C. ADD INDEX
D. BUILD INDEX
Correct Answer: A
Explanation: The CREATE INDEX statement is used to create an index, which speeds up data retrieval operations on a table.

Question 14:
What is the effect of the DISTINCT keyword in a MySQL SELECT statement?
A. It sorts the results
B. It removes duplicate rows from the result set
C. It limits the number of rows returned
D. It joins tables
Correct Answer: B
Explanation: DISTINCT ensures that only unique rows are returned in the query results, eliminating duplicates.

Question 15:
In MySQL, how do you escape a single quote in a string?
A. Using double quotes
B. Using a backslash before the single quote
C. Using brackets
D. It cannot be escaped
Correct Answer: B
Explanation: To include a single quote in a string, precede it with a backslash (\), e.g., ‘O\’Reilly’.

Question 16:
What does the LIMIT clause do in a MySQL query?
A. Limits the number of rows returned
B. Limits the size of the database
C. Limits the length of strings
D. Limits the transaction time
Correct Answer: A
Explanation: The LIMIT clause restricts the number of rows returned in the result set, often used for pagination.

Question 17:
Which MySQL data type is suitable for storing binary data like images?
A. TEXT
B. BLOB
C. VARCHAR
D. INT
Correct Answer: B
Explanation: BLOB (Binary Large Object) is used to store large amounts of binary data, such as images or files.

Question 18:
What is the purpose of the WHERE clause in a MySQL UPDATE statement?
A. To specify which columns to update
B. To filter which rows to update
C. To order the results
D. To group the data
Correct Answer: B
Explanation: The WHERE clause in an UPDATE statement specifies the conditions for which rows should be modified.

Question 19:
In MySQL, what command is used to grant privileges to a user?
A. GRANT
B. GIVE
C. ASSIGN
D. PERMIT
Correct Answer: A
Explanation: The GRANT statement is used to assign privileges to MySQL users for specific databases or tables.

Question 20:
Which MySQL function is used to concatenate strings?
A. CONCAT
B. JOIN
C. MERGE
D. COMBINE
Correct Answer: A
Explanation: The CONCAT function combines two or more strings into one string.