MCQs for Class 15: Working with Databases - Part 1

 Multiple Choice Questions (MCQs)

Working with Databases - Part 1

1. What is MySQL?
• A) A programming language
• B) A web server
• C) A relational database management system
• D) An operating system
  Answer: C
2. Which PHP function is used to connect to a MySQL database?
• A) mysqli_connect()
• B) mysql_connect()
• C) db_connect()
• D) connect_db()
  Answer: A
3. What SQL command is used to retrieve data from a database?
• A) GET
• B) SELECT
• C) PULL
• D) SHOW
  Answer: B
4. Which of the following is a valid SQL statement to create a table?
• A) CREATE TABLE users (id INT, name VARCHAR(50));
• B) NEW TABLE users (id INT, name VARCHAR(50));
• C) MAKE TABLE users (id INT, name VARCHAR(50));
• D) TABLE CREATE users (id INT, name VARCHAR(50));
  Answer: A
5. What does SQL stand for?
• A) Structured Query Language
• B) Simple Query Language
• C) Standard Query Language
• D) Syntax Query Language
  Answer: A
6. Which operator is used in SQL to search for a specified pattern in a column?
• A) LIKE
• B) FIND
• C) MATCH
• D) SEARCH
  Answer: A
7. Which PHP function is used to execute a query on a MySQL database?
• A) mysql_query()
• B) mysqli_query()
• C) execute_query()
• D) db_query()
  Answer: B
8. What SQL command is used to update existing records in a table?
• A) MODIFY
• B) CHANGE
• C) UPDATE
• D) SET
  Answer: C
9. Which SQL clause is used to filter records?
• A) WHERE
• B) FILTER
• C) HAVING
• D) SELECT
  Answer: A
10. What is the default port number for MySQL?
• A) 3306
• B) 8080
• C) 5432
• D) 1521
  Answer: A
11. Which SQL statement is used to delete data from a database?
• A) DELETE
• B) REMOVE
• C) DROP
• D) TRUNCATE
  Answer: A
12. What keyword is used to create a new record in a database table?
• A) ADD
• B) INSERT
• C) NEW
• D) CREATE
  Answer: B
13. Which function fetches a result row as an associative array in PHP?
• A) fetch_array()
• B) mysqli_fetch_assoc()
• C) fetch_assoc()
• D) fetch_row()
  Answer: B
14. What does the acronym "CRUD" stand for in database operations?
• A) Create, Read, Update, Delete
• B) Create, Replace, Update, Delete
• C) Create, Read, Upload, Delete
• D) Create, Read, Undo, Delete
  Answer: A
15. Which SQL function is used to count the number of rows in a table?
• A) COUNT()
• B) SUM()
• C) TOTAL()
• D) ADD()
  Answer: A
16. In SQL, what does the GROUP BY clause do?
• A) Groups rows that have the same values in specified columns into summary rows
• B) Sorts the results of a query
• C) Limits the number of rows returned
• D) Filters the results of a query
  Answer: A
17. What is a primary key in a database?
• A) A column that can have null values
• B) A unique identifier for a record in a table
• C) A column that allows duplicate values
• D) A special column that stores images
  Answer: B
18. Which SQL command is used to create an index on a table?
• A) CREATE INDEX
• B) ADD INDEX
• C) MAKE INDEX
• D) BUILD INDEX
  Answer: A
19. Which of the following SQL statements will return all columns from the "employees" table?
• A) SELECT * FROM employees;
• B) GET ALL FROM employees;
• C) SELECT ALL FROM employees;
• D) SELECT employees;
  Answer: A
20. What PHP function closes the connection to a MySQL database?
• A) mysqli_close()
• B) close_connection()
• C) db_close()
• D) disconnect()
  Answer: A
21. Which SQL statement is used to add a new column to an existing table?
• A) ALTER TABLE table_name ADD column_name datatype;
• B) UPDATE TABLE table_name ADD column_name datatype;
• C) MODIFY TABLE table_name ADD column_name datatype;
• D) CREATE TABLE table_name ADD column_name datatype;
  Answer: A
22. What will be the result of the SQL statement SELECT DISTINCT department FROM employees;?
• A) Returns all departments including duplicates
• B) Returns unique department names
• C) Returns the total number of departments
• D) Returns the first department only
  Answer: B
23. What does the LIMIT clause do in SQL?
• A) Restricts the number of rows returned by a query
• B) Sorts the results
• C) Filters the results
• D) Groups the results
  Answer: A
24. In SQL, what is the purpose of the HAVING clause?
• A) To filter records after aggregation
• B) To filter records before aggregation
• C) To sort records
• D) To create a new table
  Answer: A
25. Which of the following data types is not valid in MySQL?
• A) INT
• B) VARCHAR
• C) BOOLEAN
• D) OBJECT
  Answer: D
26. Which function in PHP is used to escape special characters in a string for use in an SQL statement?
• A) mysqli_real_escape_string()
• B) escape_string()
• C) addslashes()
• D) sanitize()
  Answer: A
27. Which SQL command is used to remove a table from a database?
• A) DROP TABLE
• B) DELETE TABLE
• C) REMOVE TABLE
• D) TRUNCATE TABLE
  Answer: A
28. What will the SQL query SELECT * FROM employees WHERE salary IS NOT NULL; return?
• A) All employees with a salary
• B) All employees with a null salary
• C) Employees with a salary of zero
• D) All employees
  Answer: A
29. Which of the following statements is used to create a database in MySQL?
• A) CREATE DATABASE my_database;
• B) NEW DATABASE my_database;
• C) ADD DATABASE my_database;
• D) DATABASE CREATE my_database;
  Answer: A
30. What is the purpose of the JOIN clause in SQL?
• A) To combine rows from two or more tables based on a related column
• B) To filter results
• C) To sort results
• D) To group results
  Answer: A
31. Which type of join returns all records from the left table and matched records from the right table?
• A) INNER JOIN
• B) LEFT JOIN
• C) RIGHT JOIN
• D) FULL JOIN
  Answer: B
32. What keyword is used to define a foreign key in SQL?
• A) FOREIGN
• B) REFERENCES
• C) KEY
• D) LINK
  Answer: B
33. Which function retrieves the last inserted ID in MySQL?
• A) mysqli_last_insert_id()
• B) last_insert_id()
• C) get_last_id()
• D) retrieve_id()
  Answer: A
34. Which of the following statements will correctly count the number of records in a table?
• A) SELECT COUNT(*) FROM employees;
• B) SELECT NUM(*) FROM employees;
• C) COUNT(*) IN employees;
• D) SELECT TOTAL(*) FROM employees;
  Answer: A
35. What will the query SELECT * FROM employees WHERE department = 'HR' AND salary > 50000; return?
• A) Employees in HR with a salary greater than 50000
• B) All employees in HR
• C) All employees with a salary greater than 50000
• D) No results
  Answer: A
36. What is the purpose of the ORDER BY clause in SQL?
• A) To sort the results
• B) To group the results
• C) To filter the results
• D) To limit the results
  Answer: A
37. Which PHP function is used to get the number of rows returned by a query?
• A) mysqli_num_rows()
• B) count_rows()
• C) row_count()
• D) get_rows()
  Answer: A
38. What does the acronym "SQL" refer to in database management?
• A) Structured Query Language
• B) Simple Query Language
• C) Standard Query Language
• D) System Query Language
  Answer: A
39. Which command is used to change the structure of an existing table?
• A) ALTER TABLE
• B) MODIFY TABLE
• C) UPDATE TABLE
• D) CHANGE TABLE
  Answer: A
40. What is the purpose of the TRUNCATE command in SQL?
• A) To delete all rows in a table without logging individual row deletions
• B) To remove a table
• C) To drop a database
• D) To update records
  Answer: A
41. Which SQL clause is used to group rows that have the same values?
• A) GROUP BY
• B) ORDER BY
• C) JOIN
• D) HAVING
  Answer: A
42. Which MySQL function would you use to concatenate two strings?
• A) CONCAT()
• B) JOIN()
• C) ADD()
• D) MERGE()
  Answer: A
43. What will the following SQL statement do: SELECT name FROM employees WHERE name LIKE 'A%';?
• A) Return names that start with 'A'
• B) Return all names
• C) Return names that end with 'A'
• D) Return names that contain 'A'
  Answer: A
44. Which command is used to change data in a table?
• A) UPDATE
• B) MODIFY
• C) CHANGE
• D) ALTER
  Answer: A
45. In MySQL, which keyword is used to specify a constraint?
• A) CONSTRAINT
• B) LIMIT
• C) KEY
• D) UNIQUE
  Answer: A
46. What does the NULL value represent in a database?
• A) A non-existent value
• B) A value of zero
• C) A string of length zero
• D) A unique identifier
  Answer: A
47. Which of the following is a valid way to insert multiple records in a single SQL statement?
• A) INSERT INTO employees (name) VALUES ('John'), ('Jane');
• B) INSERT INTO employees (name) ADD ('John'), ('Jane');
• C) INSERT INTO employees (name) NEW ('John'), ('Jane');
• D) INSERT MULTIPLE INTO employees (name) VALUES ('John'), ('Jane');
  Answer: A
48. Which MySQL command is used to view all databases?
• A) SHOW DATABASES;
• B) LIST DATABASES;
• C) VIEW DATABASES;
• D) DISPLAY DATABASES;
  Answer: A
49. What is the purpose of the DEFAULT keyword in SQL?
• A) To specify a default value for a column
• B) To define a primary key
• C) To set constraints
• D) To create indexes
  Answer: A
50. What does the DISTINCT keyword do in an SQL query?
• A) Returns unique values
• B) Returns all values including duplicates
• C) Filters results
• D) Sorts results
  Answer: A
51. Which of the following SQL statements is correct?
• A) SELECT id, name FROM employees;
• B) GET id, name FROM employees;
• C) FETCH id, name FROM employees;
• D) SHOW id, name FROM employees;
  Answer: A
52. What is the correct syntax to delete a table in SQL?
• A) DROP TABLE table_name;
• B) DELETE TABLE table_name;
• C) REMOVE TABLE table_name;
• D) TRUNCATE TABLE table_name;
  Answer: A
53. Which SQL function returns the highest value in a column?
• A) MAX()
• B) HIGHEST()
• C) TOP()
• D) BEST()
  Answer: A
54. What is the purpose of the FOREIGN KEY constraint?
• A) To maintain referential integrity between two tables
• B) To enforce uniqueness of a column
• C) To set a default value for a column
• D) To define an index
  Answer: A
55. Which command would you use to rename a table?
• A) RENAME TABLE old_name TO new_name;
• B) CHANGE TABLE old_name TO new_name;
• C) ALTER TABLE old_name NAME new_name;
• D) UPDATE TABLE old_name SET NAME new_name;
  Answer: A
56. What does the SQL command TRUNCATE TABLE employees; do?
• A) Removes all records from the employees table without logging individual deletions
• B) Deletes the employees table
• C) Updates all records in the employees table
• D) Creates a new employees table
  Answer: A
57. Which clause is used to filter records after grouping in SQL?
• A) HAVING
• B) WHERE
• C) FILTER
• D) GROUP BY
  Answer: A
58. What will be the result of the SQL query SELECT * FROM employees ORDER BY salary DESC;?
• A) Returns employees sorted by salary in descending order
• B) Returns employees sorted by salary in ascending order
• C) Returns employees without sorting
• D) Returns an error
  Answer: A
59. What is a composite key?
• A) A key that consists of two or more columns
• B) A key that is generated automatically
• C) A key that is created by the user
• D) A unique key that allows null values
  Answer: A
60. Which of the following functions retrieves data from a result set in PHP?
• A) mysqli_fetch_array()
• B) fetch_data()
• C) get_data()
• D) retrieve_array()
  Answer: A
61. What does the SQL command INSERT INTO employees (name, salary) VALUES ('Alice', 60000); do?
• A) Adds a new employee with the name 'Alice' and salary 60000
• B) Updates the salary of 'Alice' to 60000
• C) Deletes the employee named 'Alice'
• D) Creates a new employees table
  Answer: A
62. Which of the following SQL commands is used to change a column's datatype?
• A) ALTER TABLE table_name MODIFY column_name new_datatype;
• B) CHANGE TABLE table_name ALTER column_name new_datatype;
• C) MODIFY TABLE table_name CHANGE column_name new_datatype;
• D) UPDATE TABLE table_name SET column_name new_datatype;
  Answer: A
63. What does the AND operator do in SQL?
• A) Combines two conditions and returns true if both are true
• B) Combines two conditions and returns true if either is true
• C) Returns all records
• D) Filters results based on a single condition
  Answer: A
64. What is the output of the following SQL query: SELECT UPPER(name) FROM employees;?
• A) Returns names in uppercase
• B) Returns names in lowercase
• C) Returns the first name only
• D) Returns an error
  Answer: A
65. Which MySQL command is used to add constraints to a column?
• A) ALTER TABLE table_name ADD CONSTRAINT constraint_name;
• B) MODIFY TABLE table_name ADD CONSTRAINT constraint_name;
• C) ADD CONSTRAINT table_name column_name;
• D) CREATE CONSTRAINT table_name column_name;
  Answer: A
66. What is a transaction in SQL?
• A) A set of SQL commands executed as a single unit of work
• B) A method to sort data
• C) A command to create a new table
• D) A command to delete records
  Answer: A
67. What does the SQL command SELECT name FROM employees WHERE salary BETWEEN 50000 AND 80000; do?
• A) Retrieves names of employees with a salary between 50000 and 80000
• B) Retrieves names of employees with a salary below 50000
• C) Retrieves names of employees with a salary above 80000
• D) Retrieves all employee names
  Answer: A
68. Which of the following is a valid SQL comment?
• A) -- This is a comment
• B) // This is a comment
• C) /* This is a comment */
• D) Both A and C
  Answer: D
69. Which SQL function is used to find the number of rows that match a specified criterion?
• A) COUNT()
• B) TOTAL()
• C) SUM()
• D) MAX()
  Answer: A
70. What will the following SQL query return: SELECT AVG(salary) FROM employees;?
• A) The average salary of employees
• B) The total salary of employees
• C) The highest salary of employees
• D) The lowest salary of employees
  Answer: A
71. What is a primary key?
• A) A unique identifier for a record in a table
• B) A key that allows duplicate values
• C) A key that can contain null values
• D) A foreign key in another table
  Answer: A
72. What does the AS keyword do in SQL?
• A) Renames a column or table
• B) Defines a primary key
• C) Specifies a foreign key
• D) Creates a new table
  Answer: A
73. Which of the following SQL commands is used to create a new table?
• A) CREATE TABLE table_name (column1 datatype, column2 datatype);
• B) NEW TABLE table_name (column1 datatype, column2 datatype);
• C) ADD TABLE table_name (column1 datatype, column2 datatype);
• D) MAKE TABLE table_name (column1 datatype, column2 datatype);
  Answer: A
74. Which SQL command is used to remove a database?
• A) DROP DATABASE database_name;
• B) DELETE DATABASE database_name;
• C) REMOVE DATABASE database_name;
• D) CLEAR DATABASE database_name;
  Answer: A
75. What does the SQL command SELECT * FROM employees WHERE name IS NULL; do?
• A) Retrieves records where the name is null
• B) Retrieves records where the name is not null
• C) Retrieves all records
• D) Retrieves records with a blank name
  Answer: A
76. Which SQL clause is used to sort the results of a query?
• A) ORDER BY
• B) SORT BY
• C) GROUP BY
• D) FILTER BY
  Answer: A
77. What is the purpose of the JOIN clause in SQL?
• A) To combine rows from two or more tables based on a related column
• B) To delete rows from a table
• C) To update rows in a table
• D) To group rows in a table
  Answer: A
78. What will the following SQL statement do: SELECT name FROM employees WHERE salary IS NOT NULL;?
• A) Retrieve names of employees with a salary
• B) Retrieve names of employees without a salary
• C) Retrieve all employee names
• D) Retrieve names of employees with a null salary
  Answer: A
79. What does the IN operator do in SQL?
• A) Checks if a value matches any value in a list
• B) Checks if a value is equal to another value
• C) Checks if a value is not in a list
• D) Compares two values
  Answer: A
80. Which of the following is used to create an index on a table column?
• A) CREATE INDEX index_name ON table_name (column_name);
• B) ADD INDEX index_name ON table_name (column_name);
• C) NEW INDEX index_name ON table_name (column_name);
• D) MAKE INDEX index_name ON table_name (column_name);
  Answer: A
81. What is the correct syntax to create a view in SQL?
• A) CREATE VIEW view_name AS SELECT column1, column2 FROM table_name;
• B) NEW VIEW view_name AS SELECT column1, column2 FROM table_name;
• C) CREATE VIEW view_name SELECT column1, column2 FROM table_name;
• D) MAKE VIEW view_name AS SELECT column1, column2 FROM table_name;
  Answer: A
82. Which SQL command is used to modify existing data in a table?
• A) UPDATE
• B) CHANGE
• C) EDIT
• D) MODIFY
  Answer: A
83. What does the OR operator do in SQL?
• A) Combines two conditions and returns true if either is true
• B) Combines two conditions and returns true if both are true
• C) Filters results based on a single condition
• D) Returns all records
  Answer: A
84. What does the LIKE operator do in SQL?
• A) Searches for a specified pattern in a column
• B) Checks if a column is null
• C) Checks for exact matches
• D) Filters based on a condition
  Answer: A
85. Which SQL keyword is used to limit the number of records returned?
• A) LIMIT
• B) TOP
• C) MAX
• D) RESTRICT
  Answer: A
86. Which of the following commands would you use to check the structure of a table?
• A) DESCRIBE table_name;
• B) SHOW table_name;
• C) LIST table_name;
• D) VIEW table_name;
  Answer: A
87. Which SQL command is used to remove a column from a table?
• A) ALTER TABLE table_name DROP column_name;
• B) DELETE COLUMN column_name FROM table_name;
• C) REMOVE column_name FROM table_name;
• D) DROP column_name FROM table_name;
  Answer: A
88. What will the SQL statement SELECT name, COUNT(*) FROM employees GROUP BY name; return?
• A) The count of records for each employee name
• B) All employee names
• C) The total count of employees
• D) An error
  Answer: A
89. What is the purpose of the UNION operator in SQL?
• A) Combines the results of two or more SELECT statements
• B) Filters records
• C) Sorts results
• D) Joins tables
  Answer: A
90. What does the EXISTS keyword do in SQL?
• A) Checks for the existence of any record in a subquery
• B) Deletes records from a table
• C) Updates records in a table
• D) Creates a new table
  Answer: A
91. Which command is used to create a temporary table?
• A) CREATE TEMPORARY TABLE table_name;
• B) NEW TEMPORARY TABLE table_name;
• C) TEMP TABLE table_name;
• D) MAKE TEMPORARY TABLE table_name;
  Answer: A
92. What does the CASE statement do in SQL?
• A) Allows conditional logic in a query
• B) Joins two tables
• C) Filters records
• D) Sorts results
  Answer: A
93. What is the result of executing SELECT * FROM employees LIMIT 5;?
• A) Retrieves the first 5 records from the employees table
• B) Retrieves all records from the employees table
• C) Retrieves 5 records randomly
• D) Returns an error
  Answer: A
94. Which of the following is a valid way to perform a left join?
• A) SELECT * FROM table1 LEFT JOIN table2 ON table1.id = table2.id;
• B) SELECT * FROM table1 RIGHT JOIN table2 ON table1.id = table2.id;
• C) SELECT * FROM table1 JOIN table2;
• D) SELECT * FROM table1 INNER JOIN table2;
  Answer: A
95. What does the SQL command SELECT COUNT(DISTINCT column_name) FROM table_name; do?
• A) Counts the number of unique values in a column
• B) Counts all values in a column
• C) Counts only null values in a column
• D) Counts all records in the table
  Answer: A
96. What is the correct way to comment a single line in SQL?
• A) -- This is a comment
• B) // This is a comment
• C) /* This is a comment */
• D) ** This is a comment
  Answer: A
97. Which SQL statement is used to retrieve unique records?
• A) SELECT DISTINCT
• B) SELECT UNIQUE
• C) SELECT DIFFERENT
• D) SELECT SEPARATE
  Answer: A
98. What will the SQL command SELECT product_name FROM products ORDER BY price DESC; do?
• A) Retrieves product names sorted by price in descending order
• B) Retrieves product names sorted by price in ascending order
• C) Retrieves all product names
• D) Retrieves product names without sorting
  Answer: A
99. What is the purpose of the TRUNCATE command?
• A) Deletes all records from a table without logging individual row deletions
• B) Deletes specific records from a table
• C) Removes the table structure
• D) Renames a table
  Answer: A
100. Which of the following commands is used to remove all records from a table without removing the table itself? - A) TRUNCATE table_name; - B) DELETE FROM table_name; - C) DROP table_name; - D) REMOVE table_name;
     Answer: A