Learn SQL: A Comprehensive Guide for Beginners

Question 1

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

Accepted Answer

UPDATE

Answer

INSERT

Answer

SELECT

Answer

DELETE

Question 2

Which of the following SQL functions is used to return the number of rows in a table?

Accepted Answer

COUNT(*)

Answer

SUM()

Answer

AVG()

Answer

MAX()

Question 3

What is the purpose of using a transaction in SQL?

Accepted Answer

To ensure that a set of SQL statements is executed as a single unit

Answer

To improve the performance of SQL queries

Answer

To create a backup of the database

Answer

To delete all rows from a table

Question 4

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

Accepted Answer

To specify which rows to retrieve

Answer

To specify which columns to retrieve

Answer

To create a new table

Answer

To update existing data

Question 5

Which of the following data types is used to store whole numbers in SQL?

Accepted Answer

INT

Answer

VARCHAR

Answer

FLOAT

Answer

BOOLEAN

Question 6

What is the purpose of using an SQL index?

Accepted Answer

To improve query performance

Answer

To reduce data redundancy

Answer

To create a backup of a database

Answer

To delete data from a database

Question 7

Which SQL statement is used to retrieve all records from a table named 'Customers'?

Accepted Answer

SELECT * FROM Customers;

Answer

SELECT * FROM Clients;

Answer

SELECT ALL Customers;

Answer

GET ALL FROM Customers;

Question 8

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

Accepted Answer

To sort query results in ascending or descending order.

Answer

To group query results by a particular field.

Answer

To filter query results based on a condition.

Answer

To insert new records into a table.

Question 9

What is the purpose of a database schema in SQL?

Accepted Answer

To define the structure and relationships of tables in a database

Answer

To store actual data in the database

Answer

To provide a graphical user interface for database interaction

Answer

To optimize query performance

Question 10

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

Accepted Answer

INSERT INTO Orders (OrderID, CustomerID, ProductID) VALUES (1, 1, 1);

Answer

SELECT * FROM Orders;

Answer

CREATE TABLE Orders (OrderID INT, CustomerID INT, ProductID INT);

Answer

GRANT SELECT ON Orders TO user1;

Question 11

Distinguish between a view and a table in SQL.

Accepted Answer

A view is a virtual table derived from existing tables, while a table is a physical data storage structure.

Answer

A table is a virtual table derived from existing views, while a view is a physical data storage structure.

Answer

Both views and tables store data, but views are more efficient for complex queries.

Answer

Views and tables are essentially the same.

Question 12

Which SQL statement is used to retrieve data from a table?

Accepted Answer

SELECT

Answer

INSERT

Answer

UPDATE

Answer

DELETE

Question 13

What is the key difference between a clustered and non-clustered index in SQL Server?

Accepted Answer

Clustered indexes physically sort the data on disk, while non-clustered indexes do not

Answer

Non-clustered indexes physically sort the data on disk, while clustered indexes do not

Answer

Clustered indexes improve performance for range queries, while non-clustered indexes improve performance for equality queries

Answer

Non-clustered indexes improve performance for range queries, while clustered indexes improve performance for equality queries

Question 14

Which SQL statement is used to retrieve data from a table?

Accepted Answer

SELECT

Answer

INSERT

Answer

UPDATE

Answer

DELETE

Question 15

Which keyword is used to create a table in SQL?

Accepted Answer

CREATE

Answer

TABLE

Answer

DATA

Answer

INSERT

Question 16

What is the purpose of the PRIMARY KEY constraint in SQL?

Accepted Answer

To ensure each row in a table has a unique identifier

Answer

To prevent duplicate values from being inserted into a column

Answer

To establish relationships between tables

Answer

To specify the data type of a column

Question 17

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

Accepted Answer

ALTER TABLE

Answer

EDIT TABLE

Answer

CHANGE TABLE

Answer

MODIFY TABLE

Question 18

Which of the following is a benefit of using indexes in SQL queries?

Accepted Answer

Indexes can significantly improve query performance by speeding up data retrieval.

Answer

Indexes guarantee that data will always be sorted in a specific order.

Answer

Indexes prevent duplicate values from being inserted into a table.

Answer

Indexes automatically update themselves when data is modified.

Question 19

Which SQL statement is used to retrieve data from a database table?

Accepted Answer

SELECT

Answer

INSERT

Answer

UPDATE

Answer

DELETE

Question 20

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

Accepted Answer

To filter the returned data based on specific conditions

Answer

To sort the returned data in a particular order

Answer

To group the returned data by shared values

Answer

To limit the number of rows retrieved

Question 21

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

Accepted Answer

VARCHAR(50)

Answer

INT

Answer

DATE

Answer

BOOLEAN

Question 22

Describe the key difference between 'PRIMARY KEY' and 'FOREIGN KEY' constraints in SQL.

Accepted Answer

A PRIMARY KEY uniquely identifies each row in a table, while a FOREIGN KEY references a primary key in another table.

Answer

A FOREIGN KEY uniquely identifies each row in a table, while a PRIMARY KEY references a foreign key in another table.

Answer

Both PRIMARY KEY and FOREIGN KEY constraints ensure data integrity, but PRIMARY KEY is used for unique identification and FOREIGN KEY is used for referencing.

Answer

There is no fundamental difference between PRIMARY KEY and FOREIGN KEY constraints.

Question 23

Which SQL function is used to calculate the average value of a numeric column?

Accepted Answer

AVG()

Answer

SUM()

Answer

COUNT()

Answer

MAX()

Question 24

What is the main purpose of using a 'JOIN' operation in SQL?

Accepted Answer

To merge data from multiple tables based on matching columns

Answer

To create a new table by combining data from multiple tables

Answer

To delete duplicate rows from a table

Answer

To update data in multiple tables simultaneously

Question 25

What is the primary role of a database management system (DBMS) in SQL operations?

Accepted Answer

Managing and controlling database access

Answer

Providing a user-friendly interface for database interaction

Answer

Translating SQL statements into machine-readable code

Answer

Storing and retrieving data from the database

Question 26

What are the key advantages of using stored procedures and functions in SQL?

Accepted Answer

Reduced code duplication, improved performance, and simplified maintenance

Answer

Increased flexibility, enhanced security, and centralized data management

Answer

Improved data integrity, simplified user interface, and enhanced data visualization

Question 27

In SQL databases, what ethical and legal considerations should be taken into account when handling personal data?

Accepted Answer

Obtain explicit consent before collecting personal data.

Answer

Personal data can be used for any purpose after collection.

Answer

Indefinite storage of personal data is generally acceptable.

Question 28

To add a new row to the 'Orders' table, which SQL statement would you use?

Accepted Answer

INSERT INTO Orders (OrderID, CustomerID, OrderDate) VALUES (1001, 1, '2023-03-08')

Answer

ADD ROW TO Orders (OrderID, CustomerID, OrderDate) VALUES (1001, 1, '2023-03-08')

Answer

CREATE ROW IN Orders (OrderID, CustomerID, OrderDate) VALUES (1001, 1, '2023-03-08')

Answer

NEW ROW IN Orders (OrderID, CustomerID, OrderDate) VALUES (1001, 1, '2023-03-08')

Question 29

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

Accepted Answer

To filter results based on specified conditions

Answer

To sort results in ascending order

Answer

To group results by a specific field

Answer

To delete rows from a table

Question 30

Explain the distinction between a primary key and a foreign key in a relational database.

Accepted Answer

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

Answer

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

Answer

Both primary keys and foreign keys are used to uniquely identify rows in a table

Answer

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

Question 31

What is the purpose of using a 'GROUP BY' clause in an SQL statement?

Accepted Answer

To group results by a specific field

Answer

To sort results in ascending order

Answer

To filter results based on specified conditions

Answer

To delete rows from a table

Question 32

Which of the following is the correct syntax to create a table named 'student_info' with four columns: 'student_id' (integer), 'name' (text), 'age' (integer), and 'address' (text)?

Accepted Answer

CREATE TABLE student_info (student_id INT, name TEXT, age INTEGER, address TEXT)

Answer

CREATE TABLE student_info (student_id NUMERIC, name STRING, age INT, address VARCHAR)

Answer

CREATE TABLE student_info (student_id INTEGER, name VARCHAR, age NUMERIC, address TEXT)

Answer

CREATE TABLE student_info (student_id INT, name CHAR, age INTEGER, address VARCHAR)

Question 33

Which SQL statement is used to retrieve all records from the 'student_info' table?

Accepted Answer

SELECT * FROM student_info

Answer

GET * FROM student_info

Answer

READ * FROM student_info

Answer

FETCH * FROM student_info

Question 34

Which of the following is the correct syntax to insert a new record into the 'student_info' table?

Accepted Answer

INSERT INTO student_info (student_id, name, age, address) VALUES (101, 'John Smith', 18, '123 Main Street')

Answer

ADD INTO student_info (student_id, name, age, address) VALUES (101, 'John Smith', 18, '123 Main Street')

Answer

INSERT INTO student_info SET student_id = 101, name = 'John Smith', age = 18, address = '123 Main Street'

Answer

ADD INTO student_info SET student_id = 101, name = 'John Smith', age = 18, address = '123 Main Street'

Question 35

Which SQL statement is used to update the 'age' of a student with 'student_id' 101 to 19?

Accepted Answer

UPDATE student_info SET age = 19 WHERE student_id = 101

Answer

CHANGE student_info SET age = 19 WHERE student_id = 101

Answer

MODIFY student_info SET age = 19 WHERE student_id = 101

Answer

ALTER student_info SET age = 19 WHERE student_id = 101

Question 36

Which of the following is the correct syntax to delete a record from the 'student_info' table where 'student_id' is 102?

Accepted Answer

DELETE FROM student_info WHERE student_id = 102

Answer

REMOVE FROM student_info WHERE student_id = 102

Answer

ERASE FROM student_info WHERE student_id = 102

Answer

DROP FROM student_info WHERE student_id = 102

Question 37

Which data type is appropriate for storing a student's name?

Accepted Answer

TEXT

Answer

INTEGER

Answer

REAL

Answer

BLOB

Question 38

Which of the following is a function to calculate the average of a numeric column?

Accepted Answer

AVG()

Answer

SUM()

Answer

COUNT()

Answer

MAX()

Question 39

Which SQL statement is used to retrieve data from a database table?

Accepted Answer

SELECT

Answer

INSERT

Answer

UPDATE

Answer

DELETE

Question 40

Which clause in a SQL statement is used to specify the conditions for retrieving data?

Accepted Answer

WHERE

Answer

ORDER BY

Answer

FROM

Question 41

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

Accepted Answer

=

Answer

!=

Answer

<

Answer

>

Question 42

What is the primary purpose of a primary key in a database table?

Accepted Answer

To uniquely identify each row

Answer

To store the most important data

Answer

To optimize query performance

Answer

To enforce data integrity

Question 43

Which SQL statement is used to add a new row to a database table?

Accepted Answer

INSERT INTO

Answer

DELETE

Answer

SELECT FROM

Answer

UPDATE

Question 44

What is the key difference between an INNER JOIN and an OUTER JOIN in SQL?

Accepted Answer

An OUTER JOIN includes rows that do not match in the other table, while an INNER JOIN only includes matching rows

Answer

An INNER JOIN is more efficient than an OUTER JOIN

Question 45

Which SQL function can be used to calculate the average of a set of values?

Accepted Answer

AVG()

Answer

SUM()

Answer

MIN()

Answer

COUNT()

Question 46

Which SQL statement is used to create a new database?

Accepted Answer

CREATE DATABASE

Answer

CREATE TABLE

Answer

INSERT INTO