SQL Learning Quizzes: Test Your Database Query Skills

Question 1

Which of the following data types is not supported by SQL?

Accepted Answer

ARRAY

Answer

INTEGER

Answer

VARCHAR

Answer

BOOLEAN

Question 2

What is a primary advantage of data normalization in SQL database design?

Accepted Answer

Reduces data duplication

Answer

Complicates data structure

Answer

Slows down query performance

Question 3

Write an SQL query to find the top 5 product categories with the highest total sales. Display the sales figures in descending order.

Accepted Answer

SELECT category, SUM(sales) AS total_sales FROM sales GROUP BY category ORDER BY total_sales DESC LIMIT 5;

Answer

SELECT category, sales FROM sales GROUP BY category ORDER BY sales DESC LIMIT 5;

Answer

SELECT SUM(sales) AS total_sales, category FROM sales GROUP BY category ORDER BY total_sales;

Question 4

What's the primary purpose of a PRIMARY KEY constraint in SQL?

Accepted Answer

Ensuring unique values in a column

Answer

Preventing null values

Answer

Establishing table relationships

Answer

Boosting query performance

Question 5

The 'WHERE' clause in an SQL statement is primarily used for what purpose?

Accepted Answer

Selecting specific rows from a table based on specified conditions

Answer

Adding new rows to a table

Answer

Updating existing rows in a table

Answer

Deleting rows from a table

Question 6

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

Accepted Answer

Encrypting and decrypting data

Answer

Storing and managing data

Answer

Manipulating and processing data

Answer

Ensuring data security and integrity

Question 7

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

Accepted Answer

Significantly improving the performance of data retrieval queries

Answer

Enhancing the security of sensitive data

Answer

Reducing the overall size of the database

Answer

Automating the process of data entry

Question 8

Which of the following is a widely used open-source relational database management system (RDBMS)?

Accepted Answer

MySQL

Answer

Oracle

Answer

Microsoft SQL Server

Answer

IBM DB2

Question 9

In SQL, what is the correct syntax for creating a new database?

Accepted Answer

CREATE DATABASE database_name

Answer

NEW DATABASE database_name

Answer

MAKE DATABASE database_name

Answer

ADD DATABASE database_name

Question 10

Which data type in SQL is suitable for storing binary data, such as images or audio files?

Accepted Answer

BLOB

Answer

TEXT

Answer

VARCHAR

Answer

INT

Question 11

The 'GROUP BY' clause in an SQL statement is primarily used for what purpose?

Accepted Answer

Grouping rows together based on the values of one or more columns

Answer

Sorting rows based on the values of one or more columns

Answer

Filtering rows based on the values of one or more columns

Answer

Updating rows based on the values of one or more columns

Question 12

Write an SQL query to retrieve customer information for customers whose account balance exceeds $500 and whose last name begins with the letter 'S'.

Accepted Answer

SELECT * FROM customers WHERE account_balance > 500 AND last_name LIKE 'S%';

Answer

SELECT * FROM customers WHERE account_balance < 500 AND last_name LIKE 'S%';

Answer

SELECT * FROM customers WHERE account_balance = 500 AND last_name LIKE 'S%';

Question 13

Which SQL data type is best suited for storing customer phone numbers, given that phone numbers can vary in length and may contain non-numeric characters like dashes or parentheses?

Accepted Answer

VARCHAR(255)

Answer

INT

Answer

CHAR(10)

Answer

DATE

Question 14

In an SQL database schema, what is the primary distinction between a table and a view?

Accepted Answer

A table stores actual data that can be modified, while a view is a virtual representation of data that cannot be modified directly.

Answer

Tables can store null values, but views cannot.

Answer

A view is always a subset of a single table.

Answer

Tables always have a primary key, while views do not.

Question 15

Which SQL command is utilized to extract data from a database table?

Accepted Answer

SELECT

Answer

INSERT

Answer

UPDATE

Answer

DELETE

Question 16

In an SQL query, what is the function of the WHERE clause?

Accepted Answer

To filter the retrieved rows

Answer

To identify the table to be queried

Answer

To arrange the results

Answer

To group the results

Question 17

Which data type in SQL is employed to represent dates and times?

Accepted Answer

DATETIME

Answer

INTEGER

Answer

STRING

Answer

BOOLEAN

Question 18

Explain the distinction between a primary key and a foreign key.

Accepted Answer

A primary key uniquely identifies a row, while a foreign key establishes a connection to another table

Answer

A foreign key uniquely identifies a row, while a primary key establishes a connection to another table

Answer

Both uniquely identify rows

Answer

Both establish connections to other tables

Question 19

Which SQL operator is used to combine multiple conditions within a WHERE clause?

Accepted Answer

AND

Answer

OR

Answer

NOT

Answer

XOR

Question 20

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

Accepted Answer

To enhance query performance

Answer

To ensure data integrity

Answer

To store data more efficiently

Answer

To back up the database

Question 21

Which SQL statement is used to create a new table in a database?

Accepted Answer

CREATE TABLE

Answer

ALTER TABLE

Answer

DROP TABLE

Answer

INSERT INTO

Question 22

Explain the difference between an INNER JOIN and an OUTER JOIN in SQL.

Accepted Answer

An INNER JOIN retrieves rows with matching values in both tables, while an OUTER JOIN retrieves all rows from one table and matching rows from the other

Answer

An OUTER JOIN retrieves rows with matching values in both tables, while an INNER JOIN retrieves all rows from one table and matching rows from the other

Answer

They both return identical results

Answer

They both join two tables

Question 23

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

Accepted Answer

AVG()

Answer

SUM()

Answer

COUNT()

Answer

MIN()

Question 24

What is the function of a transaction in SQL?

Accepted Answer

To group multiple SQL statements into a single unit of work

Answer

To lock data during modification

Answer

To reverse changes in the event of an error

Answer

To enhance database performance

Question 25

How does a foreign key constraint ensure data consistency in SQL?

Accepted Answer

It stops data from being deleted from the parent table if there are linked records in the child table.

Answer

It guarantees that data in the child table is always updated when data in the parent table changes.

Answer

It prevents duplicate data from being inserted into the child table.

Answer

It allows data to be deleted from the parent table even if there are linked records in the child table.

Question 26

Calculate the average sales amount for each product category, grouped by region, using an SQL query.

Accepted Answer

SELECT product_category, region, AVG(sales_amount) AS average_sales FROM sales_data GROUP BY product_category, region;

Answer

SELECT product_category, region, SUM(sales_amount) AS total_sales FROM sales_data GROUP BY product_category, region;

Answer

SELECT product_category, region, MAX(sales_amount) AS max_sales FROM sales_data GROUP BY product_category, region;

Answer

SELECT product_category, region, MIN(sales_amount) AS min_sales FROM sales_data GROUP BY product_category, region;

Question 27

What is the main purpose of the 'JOIN' clause in SQL, and how does it help combine data from different tables?

Accepted Answer

To merge data from multiple tables into a new table based on matching column values.

Answer

To remove duplicate rows from a table.

Answer

To sort data in a table in a specific order.

Answer

To modify data within a table.

Question 28

Which SQL statement is used to create a new table and specify its structure?

Accepted Answer

CREATE TABLE table_name (column_name data_type, ...)

Answer

ALTER TABLE table_name ADD column_name data_type

Answer

DROP TABLE table_name

Answer

INSERT INTO table_name VALUES (...)

Question 29

What is the role of the WHERE clause in an SQL query?

Accepted Answer

To filter records based on specified conditions and retrieve only relevant data

Answer

To sort the results of the query in ascending or descending order

Answer

To group the results of the query by one or more columns

Answer

To create a new table with the filtered data

Question 30

What is the definition of a primary key in an SQL table?

Accepted Answer

A unique column or set of columns that identifies each row in the table without duplicates

Answer

A column that stores the most important information in the table

Answer

A column that is used to sort the records in the table

Answer

A column that is used to store additional information about the row

Question 31

Which SQL data type is appropriate for storing dates and times?

Accepted Answer

DATE

Answer

INTEGER

Answer

FLOAT

Answer

VARCHAR

Question 32

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

Accepted Answer

INNER JOIN retrieves only matching rows from two tables, while OUTER JOIN retrieves all rows from one or both tables

Answer

INNER JOIN retrieves all rows from both tables, while OUTER JOIN retrieves only matching rows

Answer

INNER JOIN is used to combine rows from two tables, while OUTER JOIN is used to filter rows from two tables

Answer

INNER JOIN and OUTER JOIN are the same type of join

Question 33

Which SQL function is used to calculate the average value of a set of numbers?

Accepted Answer

AVG()

Answer

SUM()

Answer

COUNT()

Answer

MIN()

Question 34

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

Accepted Answer

To arrange the results of the query in ascending or descending order based on specified columns

Answer

To filter the results of the query based on certain criteria

Answer

To group the results of the query by one or more columns

Answer

To create a new table with the sorted data

Question 35

Which character is used to terminate an SQL statement?

Accepted Answer

;

Answer

.

Answer

$

Answer

#

Question 36

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

Accepted Answer

To group rows in the result based on the values in one or more columns

Answer

To sort the results of the query in ascending or descending order

Answer

To filter the results of the query based on specific conditions

Answer

To create a new table with the grouped data

Question 37

Which of the following data types in SQL is used to store dates and times?

Accepted Answer

DATE

Answer

INT

Answer

VARCHAR

Answer

BOOLEAN

Question 38

To filter rows in a SELECT statement, which clause is used?

Accepted Answer

WHERE

Answer

SELECT

Answer

ORDER BY

Answer

JOIN

Question 39

In SQL, which function is used to combine two strings?

Accepted Answer

CONCAT

Answer

ADD

Answer

JOIN

Answer

APPEND

Question 40

Which clause in SQL is used to group rows?

Accepted Answer

GROUP BY

Answer

ORDER BY

Answer

HAVING

Answer

WHERE

Question 41

To return all rows from both tables, even without matching rows, which type of join is used in SQL?

Accepted Answer

FULL JOIN

Answer

INNER JOIN

Answer

LEFT JOIN

Answer

RIGHT JOIN

Question 42

Which statement in SQL is used to modify data in a table?

Accepted Answer

UPDATE

Answer

SELECT

Answer

DELETE

Answer

INSERT

Question 43

In SQL, which term refers to the process of combining data from multiple tables that share common columns?

Accepted Answer

Joining

Answer

Normalization

Answer

Denormalization

Answer

Aggregation

Question 44

Which SQL component defines the structure of a table, including its columns and data types?

Accepted Answer

Schema

Answer

View

Answer

Procedure

Answer

Function

Question 45

What is a defining characteristic of a primary key?

Accepted Answer

Uniquely identifies each record in a table

Answer

Can contain duplicate values

Answer

References a primary key in another table

Answer

Is not crucial for maintaining data integrity

Question 46

In SQL, which data type is specifically used to represent true or false values?

Accepted Answer

BOOLEAN

Answer

INTEGER

Answer

VARCHAR

Question 47

What is the primary purpose of utilizing the 'SELECT' statement in SQL?

Accepted Answer

Retrieves data from database tables

Answer

Adds new data to database tables

Answer

Modifies data in database tables

Answer

Deletes data from database tables

Question 48

Which comparison operator in SQL is used to determine whether two values are equal?

Accepted Answer

=

Answer

-

Answer

*

Answer

+

Question 49

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

Accepted Answer

Filters the result set of a query based on specified conditions

Answer

Groups the result set of a query

Answer

Sorts the result set of a query

Answer

Limits the number of rows returned in a query

Question 50

Which Data Definition Language (DDL) statement is used to establish a new table in SQL?

Accepted Answer

CREATE TABLE

Answer

DELETE

Answer

SELECT

Answer

UPDATE

Question 51

What is the main purpose of employing an ORDER BY clause?

Accepted Answer

Sorts the result set of a query in ascending or descending order based on specified columns

Answer

Limits the number of rows returned in a query

Answer

Filters the result set of a query

Answer

Groups the result set of a query

Question 52

In SQL, which aggregate function is used to determine the highest value in a given column?

Accepted Answer

MAX()

Answer

MIN()

Answer

AVG()

Answer

SUM()

Question 53

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

Accepted Answer

Ensures that each row within a table possesses a unique identifier

Answer

Enforces relationships between multiple tables

Answer

Prevents duplicate rows from being inserted into a table

Question 54

Which join type is utilized in SQL to combine rows from two tables that share matching values in a common column?

Accepted Answer

INNER JOIN

Answer

LEFT JOIN

Answer

FULL JOIN

Answer

RIGHT JOIN

Question 55

What is the primary purpose of a subquery in SQL?

Accepted Answer

Allows for the inclusion of results from one query within another

Answer

Creates a temporary table to store query results

Answer

Updates multiple rows in a table simultaneously