SQL (Structured Query Language) Learning Quizzes for Database Management Systems

Question 1

Which SQL command is used to extract data from a table?

Accepted Answer

SELECT

Answer

INSERT

Answer

UPDATE

Answer

DELETE

Question 2

Which of the following operators is used to compare two values for equality?

Accepted Answer

=

Answer

>

Answer

<

Answer

<>

Question 3

Which SQL keyword is used to cluster rows based on shared values?

Accepted Answer

GROUP BY

Answer

ORDER BY

Answer

HAVING

Answer

DISTINCT

Question 4

What is the purpose of the 'WHERE' clause in an SQL statement?

Accepted Answer

To specify filter conditions for data retrieval or modification

Answer

To group rows based on specific criteria

Answer

To sort the result set in a specific order

Answer

To limit the number of rows returned

Question 5

What is the distinction between a primary key and a foreign key in SQL?

Accepted Answer

A primary key uniquely identifies rows in a table, while a foreign key references a primary key in another table

Answer

A primary key references a foreign key in another table, while a foreign key uniquely identifies rows in a table

Answer

A primary key and a foreign key are both used to uniquely identify rows in a table

Answer

There is no difference between a primary key and a foreign key

Question 6

Which of the following SQL commands is used to alter existing data in a table?

Accepted Answer

UPDATE

Answer

INSERT

Answer

DELETE

Answer

SELECT

Question 7

What is the purpose of implementing an index in an SQL database?

Accepted Answer

To enhance query performance by enabling faster data access

Answer

To enforce data integrity by ensuring unique values

Answer

To limit the number of rows that can be inserted or updated

Answer

To create a backup of the database table

Question 8

Which of the following SQL statements is used to create a new table?

Accepted Answer

CREATE TABLE

Answer

INSERT INTO

Answer

SELECT *

Answer

DROP TABLE

Question 9

How do you add a new column named 'Age' of type 'int' to an existing table named 'Students' using SQL?

Accepted Answer

ALTER TABLE Students ADD COLUMN Age int

Answer

ADD COLUMN Age int TO Students

Answer

ALTER Students ADD Age int

Answer

CREATE COLUMN Age int IN Students

Question 10

How does creating an index on a frequently queried column enhance query performance?

Accepted Answer

Accelerates query execution by providing a direct path to data.

Answer

Improves data integrity by ensuring unique values in the indexed column.

Answer

Reduces storage space by compressing indexed data.

Answer

Eliminates the need for joins by pre-computing table relationships.

Question 11

In SQL, which command is specifically used for creating a new table?

Accepted Answer

CREATE TABLE

Answer

CREATE DATABASE

Answer

INSERT INTO

Answer

SELECT FROM

Question 12

What is the primary purpose of the 'WHERE' clause in an SQL statement?

Accepted Answer

To filter and retrieve specific data based on defined conditions

Answer

To create a new table with specific attributes

Answer

To modify existing data within a table

Answer

To delete data from a table

Question 13

Which data type is most suitable for storing a student's name in an SQL database?

Accepted Answer

VARCHAR

Answer

INTEGER

Answer

BOOLEAN

Answer

DATE

Question 14

Explain the distinction between a 'primary key' and a 'foreign key' in the context of database relationships.

Accepted Answer

A primary key uniquely identifies a row within a table, while a foreign key references a primary key in another table, establishing a relationship between the tables.

Answer

Both primary and foreign keys serve the same purpose of maintaining data integrity.

Answer

A foreign key uniquely identifies a row within a table, while a primary key references a foreign key in another table.

Answer

There is no significant difference between primary keys and foreign keys.

Question 15

Which SQL command is utilized to modify the structure of an existing table, such as adding or removing columns?

Accepted Answer

ALTER TABLE

Answer

CREATE TABLE

Answer

DROP TABLE

Answer

RENAME TABLE

Question 16

What is the primary benefit of using an 'index' in a database?

Accepted Answer

Improved query performance by organizing data in a specific order for efficient retrieval

Answer

Ensuring data integrity by enforcing uniqueness constraints

Answer

Storing additional information about data

Answer

Reducing the overall size of the database

Question 17

Which SQL command is specifically used to delete data from a table?

Accepted Answer

DELETE FROM

Answer

DROP TABLE

Answer

TRUNCATE TABLE

Answer

ALTER TABLE

Question 18

Which SQL function is used to determine the maximum value within a set of data?

Accepted Answer

MAX()

Answer

MIN()

Answer

AVG()

Answer

SUM()

Question 19

What is the primary purpose of a 'transaction' in the context of a database?

Accepted Answer

Grouping a series of operations into a logical unit that can be either committed (saved permanently) or rolled back (undone) as a whole, ensuring data integrity.

Answer

Preventing concurrent access to data, thereby ensuring data integrity.

Answer

Caching frequently accessed data to enhance query performance.

Answer

Storing temporary data that is not permanently saved in the database.

Question 20

To calculate the total number of students enrolled in a specific course, which SQL aggregation function should you use?

Accepted Answer

COUNT(*)

Answer

SUM(student_id)

Answer

AVG(student_id)

Answer

MIN(student_id)

Question 21

Which SQL data type is best suited for storing a student's name?

Accepted Answer

Varchar

Answer

Integer

Answer

Date

Answer

Boolean

Question 22

Which of the following is the correct syntax for creating a table named 'Employees' with columns 'EmployeeID' (INT), 'Name' (VARCHAR(255)), and 'Salary' (DECIMAL(10,2))?

Accepted Answer

CREATE TABLE Employees (EmployeeID INT, Name VARCHAR(255), Salary DECIMAL(10,2))

Answer

CREATE TABLE 'Employees' (EmployeeID INT, Name VARCHAR(255), Salary DECIMAL(10,2))

Answer

CREATE 'Employees' TABLE (EmployeeID INT, Name VARCHAR(255), Salary DECIMAL(10,2))

Answer

CREATE TABLE (EmployeeID INT, Name VARCHAR(255), Salary DECIMAL(10,2)) Employees

Question 23

Which SQL command do you use to retrieve data from a table?

Accepted Answer

SELECT

Answer

GET

Answer

READ

Answer

DISPLAY

Question 24

What is the purpose of the 'WHERE' clause in an SQL statement?

Accepted Answer

To filter results based on a specified condition

Answer

To sort results in ascending or descending order

Answer

To group results by a specific field

Answer

To limit the number of rows returned

Question 25

What is the difference between a primary key and a foreign key?

Accepted Answer

A primary key uniquely identifies each row, while a foreign key references another table's primary key.

Answer

A foreign key uniquely identifies each row, while a primary key references another table's foreign key.

Answer

Both primary keys and foreign keys are used to enforce data integrity.

Answer

There is no difference between a primary key and a foreign key.

Question 26

Which of the following is a relational database model?

Accepted Answer

Relational model

Answer

Hierarchical model

Answer

Network model

Answer

Object-oriented model

Question 27

What is the purpose of an index in a database?

Accepted Answer

To improve query performance by quickly locating data

Answer

To enforce data integrity and prevent duplicate values

Answer

To store data in a compressed format to save space

Answer

To provide a backup of the data in case of data loss

Question 28

Which of the following is NOT a function of a database management system (DBMS)?

Accepted Answer

Software development

Answer

Data storage and management

Answer

Query processing and optimization

Answer

Data security and access control

Question 29

What is the purpose of the 'ORDER BY' clause in an SQL statement?

Accepted Answer

To arrange results in ascending or descending order based on a specified field

Answer

To filter results based on a specified condition

Answer

To group results by a specific field

Answer

To limit the number of rows returned

Question 30

Which of the following SQL commands is used to update data in a table?

Accepted Answer

UPDATE

Answer

MODIFY

Answer

CHANGE

Answer

EDIT

Question 31

Which of the following is NOT a valid data type in SQL?

Accepted Answer

Array

Answer

Integer (INT)

Answer

Variable-length character string (VARCHAR)

Answer

Boolean

Question 32

What is the purpose of the SELECT statement in SQL?

Accepted Answer

Retrieve data from a table

Answer

Create a new table

Answer

Insert data into a table

Answer

Delete data from a table

Question 33

Which of the following is a logical operator in SQL?

Accepted Answer

AND

Answer

JOIN

Answer

WHERE

Answer

ORDER BY

Question 34

What is the difference between a primary key and a foreign key in SQL?

Accepted Answer

A primary key uniquely identifies each row in a table, while a foreign key references a column in another table

Answer

A foreign key uniquely identifies each row in a table, while a primary key references a column in another table

Answer

Both primary and foreign keys uniquely identify rows in a table

Answer

Both primary and foreign keys reference columns in other tables

Question 35

Which of the following commands is used to create a new database in SQL?

Accepted Answer

CREATE DATABASE

Answer

MAKE DATABASE

Answer

NEW DATABASE

Answer

BUILD DATABASE

Question 36

What is the purpose of the JOIN statement in SQL?

Accepted Answer

Combine data from multiple tables

Answer

Create a new table

Answer

Retrieve data from a table

Answer

Insert data into a table

Question 37

What is the purpose of the ORDER BY clause in SQL?

Accepted Answer

Sort the results of a query

Answer

Filter the results of a query

Answer

Group the results of a query

Answer

Join tables together

Question 38

What is the purpose of the GROUP BY clause in SQL?

Accepted Answer

Group the results of a query

Answer

Sort the results of a query

Answer

Filter the results of a query

Answer

Join tables together

Question 39

What is the primary purpose of a 'primary key' constraint in an SQL table?

Accepted Answer

Ensure each record has a unique identifier

Answer

Establish relationships between tables

Answer

Speed up data retrieval

Question 40

Explain the key differences between the 'UPDATE' and 'DELETE' commands in SQL. Provide examples to demonstrate their distinct uses.

Accepted Answer

The 'UPDATE' command modifies specific data within existing rows, while 'DELETE' removes entire rows from a table.

Answer

The 'UPDATE' command adds new rows to a table, while 'DELETE' modifies existing data.

Answer

The 'DELETE' command removes entire tables from a database, while 'UPDATE' modifies individual cells within rows.

Answer

Both 'UPDATE' and 'DELETE' commands modify existing data in a table.

Question 41

In a multi-user database environment, how do SQL's user roles enhance data protection and security?

Accepted Answer

User roles enable granular access control, restricting users to specific data and functions based on their responsibilities.

Answer

User roles provide a dedicated mechanism for monitoring and recording user actions within the database.

Answer

User roles simplify data backup and recovery processes.

Answer

User roles are not related to data protection and security in SQL database systems.

Question 42

What is the primary command used to retrieve data from a table?

Accepted Answer

SELECT

Answer

FETCH

Answer

EXTRACT

Answer

GET DATA

Question 43

Which operator is used to check if two values are equal?

Accepted Answer

=

Answer

IS

Answer

==

Answer

EQUALS

Question 44

What is the main purpose of using the GROUP BY clause?

Accepted Answer

To group rows sharing common values in specified columns and perform aggregate functions on them

Answer

To combine rows from multiple tables with matching columns

Answer

To filter the result set based on a specified condition

Answer

To sort the result set in ascending or descending order

Question 45

Which command should be used to create a new database in SQL?

Accepted Answer

CREATE DATABASE

Answer

MAKE DATABASE

Answer

NEW DATABASE

Answer

DEFINE DATABASE

Question 46

What is the purpose of utilizing the JOIN clause in SQL?

Accepted Answer

To establish relationships between rows from different tables based on common columns

Answer

To enforce data integrity constraints across multiple tables

Answer

To create a new table by combining data from multiple tables

Answer

To delete duplicate rows from a table

Question 47

What is the primary purpose of the PRIMARY KEY constraint?

Accepted Answer

To ensure the uniqueness of each row in a table by enforcing a unique value for a specified column or set of columns

Answer

To prevent duplicate values from being inserted into a specific column

Answer

To establish relationships between tables and enforce referential integrity

Answer

To set a default value for a column when no value is provided

Question 48

Which command is used to permanently remove rows from a table in SQL?

Accepted Answer

DELETE

Answer

ERASE

Answer

REMOVE

Answer

PURGE

Question 49

What is the primary function of the ORDER BY clause?

Accepted Answer

To sort the result set in ascending or descending order based on one or more specified columns

Answer

To filter the result set based on a specified condition

Answer

To group rows sharing common values in specified columns

Answer

To limit the number of rows returned in the result set

Question 50

Which syntax creates a table in SQL, defining its columns and data types?

Accepted Answer

CREATE TABLE table_name (column1 data_type, column2 data_type, ...);

Answer

CREATE table_name (column1 data_type, column2 data_type, ...);

Answer

TABLE table_name (column1 data_type, column2 data_type, ...);

Question 51

Which SQL command is designed to insert new data into an existing table?

Accepted Answer

INSERT INTO table_name (column1, column2, ...) VALUES (value1, value2, ...);

Answer

UPDATE table_name SET column1 = value1, column2 = value2, ... WHERE condition;

Answer

ADD INTO table_name (column1, column2, ...) VALUES (value1, value2, ...);

Question 52

In SQL, which operator is used to determine if two values are equal?

Accepted Answer

=

Answer

>

Answer

!=

Answer

<

Question 53

Which SQL function is employed to identify the maximum value within a data set?

Accepted Answer

MAX()

Answer

SUM()

Answer

AVG()

Answer

MIN()

Question 54

Which SQL command is utilized to retrieve specific data from a table?

Accepted Answer

SELECT

Answer

UPDATE

Answer

INSERT

Question 55

In SQL, which keyword enables the joining of two tables based on a shared column?

Accepted Answer

JOIN

Answer

INTERSECT

Answer

UNION

Question 56

Which SQL statement is used to remove data from a table based on a specified condition?

Accepted Answer

DELETE FROM table_name WHERE condition;

Answer

ERASE FROM table_name WHERE condition;

Answer

REMOVE FROM table_name WHERE condition;

Answer

DROP FROM table_name WHERE condition;

Question 57

Which SQL command is used to modify the structure of an existing table?

Accepted Answer

ALTER TABLE

Answer

MODIFY TABLE

Answer

CHANGE TABLE

Answer

EDIT TABLE