Introduction to SQL: Master the Basics of Data Management

Question 1

Which of the following is **not** a data type in SQL?

Accepted Answer

Array

Answer

Integer

Answer

String

Answer

Boolean

Question 2

Which command is primarily used to retrieve data from a database?

Accepted Answer

SELECT

Answer

INSERT

Answer

UPDATE

Answer

DELETE

Question 3

What is the main distinction between a primary key and a foreign key?

Accepted Answer

A primary key is unique for each row, while a foreign key references another table's primary key

Answer

A foreign key is unique for each row, while a primary key references another table's foreign key

Answer

They are both unique identifiers for rows in a table

Answer

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

Question 4

Which of the following is **not** an advantage of using SQL?

Accepted Answer

Compatibility with only a limited number of systems

Answer

Ability to manage large datasets efficiently

Answer

Ease of learning and use

Answer

Support for complex data manipulation

Question 5

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

Accepted Answer

To enhance the performance of queries

Answer

To ensure data integrity

Answer

To create a new table

Answer

To remove data from a table

Question 6

Which SQL command is used to create a new table?

Accepted Answer

CREATE

Answer

INSERT

Answer

SELECT

Answer

UPDATE

Question 7

What is the key difference between a view and a table?

Accepted Answer

A view is a virtual table derived from one or more tables, while a table is a physical structure that stores data

Answer

A table is a virtual table derived from one or more views, while a view is a physical structure that stores data

Answer

There is no fundamental difference between a view and a table

Answer

Both views and tables are virtual structures that store data

Question 8

How do data integrity and constraints in SQL contribute to maintaining accurate and reliable data?

Accepted Answer

They enforce rules and checks to ensure data accuracy and consistency.

Answer

They grant users unrestricted access to data throughout the database.

Answer

They are only relevant for large databases.

Answer

They can be easily added to a database after its creation.

Question 9

In SQL, which of these data types is used to store dates and time?

Accepted Answer

Date (DATE)

Answer

Integer (INT)

Answer

Variable-length character string (VARCHAR)

Answer

Logical value (BOOLEAN)

Question 10

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

Accepted Answer

Retrieving data from a table

Answer

Inserting new data into a table

Answer

Deleting rows from a table

Answer

Modifying existing data in a table

Question 11

Explain the distinction 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 may be shared among multiple rows.

Answer

A foreign key uniquely identifies each row in a table, while a primary key may be shared among multiple rows.

Answer

Primary keys are used to define relationships between tables, while foreign keys are used to identify individual rows.

Answer

Foreign keys are used to define relationships between tables, while primary keys are used to identify individual rows.

Question 12

What is the primary purpose of using a join in SQL?

Accepted Answer

Combining rows from multiple tables based on a common field

Answer

Creating a new table by merging data from two or more existing tables

Answer

Deleting rows from a table

Answer

Modifying data within a table

Question 13

What is the main purpose of using a transaction in SQL?

Accepted Answer

Combining multiple SQL statements into a single unit

Answer

Preventing other users from accessing specific rows in a table

Answer

Creating a backup of a table

Answer

Deleting all data from a table

Question 14

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

Accepted Answer

ARRAY

Answer

INTEGER

Answer

VARCHAR

Answer

DATETIME

Question 15

What is the purpose of the SELECT statement in SQL?

Accepted Answer

To retrieve data from a table

Answer

To create a new table

Answer

To insert data into a table

Answer

To delete data from a table

Question 16

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

Accepted Answer

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

Answer

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

Answer

Both primary keys and foreign keys uniquely identify rows in a table.

Answer

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

Question 17

What is the purpose of using a WHERE clause in an SQL query?

Accepted Answer

To filter the results of the query

Answer

To sort the results of the query

Answer

To group the results of the query

Answer

To limit the number of rows returned by the query

Question 18

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

Accepted Answer

To sort the results of the query

Answer

To filter the results of the query

Answer

To group the results of the query

Answer

To limit the number of rows returned by the query

Question 19

What is the purpose of using a semicolon (;) at the end of an SQL statement?

Accepted Answer

To terminate the statement

Answer

To separate multiple statements

Answer

To indicate the start of a new statement

Answer

To comment out the statement

Question 20

Which SQL statement is used to add a new employee to the 'employees' table?

Accepted Answer

INSERT INTO employees (name, email) VALUES ('John Doe', 'john.doe@example.com')

Answer

SELECT * FROM employees

Answer

UPDATE employees SET name='John Doe' WHERE id=1

Answer

DELETE FROM employees WHERE id=1

Question 21

In an SQL statement, what is the correct order of the SELECT, FROM, and WHERE clauses?

Accepted Answer

SELECT, FROM, WHERE

Answer

FROM, WHERE, SELECT

Answer

WHERE, SELECT, FROM

Answer

SELECT, WHERE, FROM

Question 22

Which of these is not a recognized data type in SQL?

Accepted Answer

LIST

Answer

INTEGER

Answer

VARCHAR

Answer

BOOLEAN

Question 23

Which SQL statement correctly deletes the record with 'CustomerID' equal to 1 from the 'Customers' table?

Accepted Answer

DELETE FROM Customers WHERE CustomerID = 1

Answer

DELETE Customer FROM Customers

Answer

DELETE Customers SET CustomerID = NULL

Answer

DELETE * FROM Customers

Question 24

Write the SQL statement to update the 'name' column of the 'student' table where the 'id' column equals 3 to 'John Doe'.

Accepted Answer

UPDATE student SET name = 'John Doe' WHERE id = 3

Answer

UPDATE student SET id = 3 WHERE name = 'John Doe'

Answer

UPDATE 3 SET name = 'John Doe' WHERE student.id = 3

Answer

UPDATE name = 'John Doe' WHERE student.id = 3

Question 25

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

Accepted Answer

ARRAY

Answer

INTEGER

Answer

VARCHAR

Answer

FLOAT

Question 26

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

Accepted Answer

=

Answer

+

Answer

>

Answer

%

Question 27

What is the main purpose of the 'WHERE' clause in SQL?

Accepted Answer

To specify conditions for filtering data

Answer

To group data by a specific column

Answer

To sort data in ascending or descending order

Answer

To limit the number of rows returned

Question 28

What is the primary function of a 'JOIN' operation in SQL?

Accepted Answer

To combine rows from two or more tables based on a common column

Answer

To create a new table from existing tables

Answer

To update data in multiple tables at once

Answer

To delete data from multiple tables at once

Question 29

What is the primary purpose of a 'GROUP BY' clause in SQL?

Accepted Answer

To group rows by a specific column and perform aggregate functions on them

Answer

To filter data based on a specific condition

Answer

To sort data in ascending or descending order

Answer

To combine rows from two or more tables

Question 30

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

Accepted Answer

To uniquely identify each row in a table

Answer

To specify the foreign key of a table

Answer

To index a table for faster data retrieval

Answer

To enforce data integrity

Question 31

Which SQL command retrieves customer names from the 'Customers' table?

Accepted Answer

SELECT

Answer

CREATE TABLE

Answer

INSERT INTO

Question 32

In SQL, what is the correct syntax for creating a table called 'Customers' with columns 'id' (integer), 'name' (text), and 'age' (integer)?

Accepted Answer

CREATE TABLE Customers (id INT, name TEXT, age INT)

Answer

TABLE Customer (id INTEGER, name TEXT, age INTEGER)

Answer

CREATE TABLE Customers {id INTEGER, name TEXT, age INTEGER}

Answer

TABLE Customer {id INT, name TEXT, age INT}

Question 33

Which SQL data type is used to store floating-point numbers?

Accepted Answer

FLOAT

Answer

INT

Answer

CHAR

Answer

VARCHAR

Question 34

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

Accepted Answer

To sort the results

Answer

To filter the results based on a condition

Answer

To group the results

Answer

To specify the table to be queried

Question 35

Which logical operator in SQL combines two conditions with an 'or' relationship?

Accepted Answer

OR

Answer

AND

Answer

NOT

Answer

XOR

Question 36

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

Accepted Answer

A primary key is a candidate key that has been chosen to uniquely identify rows in a table

Answer

A candidate key is a primary key that has not yet been chosen to uniquely identify rows in a table

Answer

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

Answer

A primary key can have duplicate values, while a candidate key cannot

Question 37

Which type of SQL join combines rows from two tables based on matching values in a specified column?

Accepted Answer

INNER JOIN

Answer

LEFT OUTER JOIN

Answer

RIGHT OUTER JOIN

Answer

FULL OUTER JOIN

Question 38

What is the purpose of using a foreign key constraint in SQL?

Accepted Answer

To ensure that data in one table is consistent with data in another table

Answer

To improve query performance

Answer

To reduce storage space

Answer

To encrypt data

Question 39

What is the difference between a materialized view and an unmaterialized view in SQL?

Accepted Answer

A materialized view is stored as a physical table, while an unmaterialized view is derived on the fly

Answer

An unmaterialized view is stored as a physical table, while a materialized view is derived on the fly

Answer

There is no difference between a materialized view and an unmaterialized view

Answer

A materialized view can be updated, while an unmaterialized view cannot

Question 40

What is the main advantage of normalizing a database?

Accepted Answer

Enhanced data consistency and integrity

Answer

Increased data redundancy for improved reliability

Answer

Simplified data querying for faster retrieval

Answer

Reduced database size for increased storage efficiency

Question 41

What's the main purpose of a database transaction?

Accepted Answer

To combine database actions into a single unit, ensuring data integrity by reversing changes if any action fails.

Answer

To make a new database object, like a table or a view.

Answer

To change data in a database, like updating or deleting records.

Answer

To get data from a database, like choosing records that meet certain criteria.

Question 42

Which SQL statement correctly retrieves all data from the 'Customers' table, filtering for customers older than 30?

Accepted Answer

SELECT * FROM Customers WHERE age > 30

Answer

GET * FROM Customers WHERE age > 30

Answer

SELECT age FROM Customers WHERE age > 30

Answer

SELECT * FROM age WHERE Customers > 30

Question 43

In SQL, what are NULL values, and how are they treated in queries and data manipulation operations?

Accepted Answer

NULL values represent the absence of a value and are distinct from both zeroes and empty strings.

Answer

NULL values indicate missing data and are treated as empty strings.

Answer

NULL values are handled as zeroes in numeric operations and empty strings in string operations.

Answer

NULL values are ignored in queries and data manipulation operations.

Question 44

What is the primary function of a SELECT statement in SQL?

Accepted Answer

To retrieve data from a table

Answer

To create a new table

Answer

To update data in a table

Answer

To delete data from a table

Question 45

Which operator is used to compare values and test for equality in SQL?

Accepted Answer

=

Answer

!=

Answer

>

Answer

<

Question 46

What is the purpose of the WHERE clause in a SQL statement?

Accepted Answer

To filter the rows to be retrieved based on specified conditions

Answer

To specify the columns to be retrieved

Answer

To sort the rows to be retrieved

Answer

To group the rows to be retrieved

Question 47

Which of the following is a common application of SQL JOIN?

Accepted Answer

Combining data from multiple related tables

Answer

Updating data in multiple tables simultaneously

Answer

Deleting data from multiple tables with a single command

Answer

Inserting data into multiple tables with a single command

Question 48

What is the primary purpose of an index in a SQL table?

Accepted Answer

To enhance query performance by providing a fast lookup mechanism

Answer

To enforce data integrity by preventing duplicate values

Answer

To reduce data redundancy by eliminating duplicate data

Answer

To make data backups faster and more efficient

Question 49

Which of the following SQL keywords is used to retrieve data from a table?

Accepted Answer

SELECT

Answer

DELETE

Answer

INSERT

Answer

UPDATE

Question 50

What data type would you use to store a person's name in an SQL database?

Accepted Answer

VARCHAR

Answer

DATE

Answer

BOOLEAN

Answer

INT

Question 51

Which SQL clause is used to filter rows based on specific conditions?

Accepted Answer

WHERE

Answer

FROM

Answer

GROUP BY

Answer

ORDER BY

Question 52

The following SQL statement: `SELECT * FROM Customers WHERE City = 'London';` will retrieve...

Accepted Answer

All columns from the Customers table where the City is 'London'.

Answer

All rows from the Customers table.

Answer

Only the City column from the Customers table.

Question 53

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

Accepted Answer

To sort the retrieved data in ascending or descending order.

Answer

To create new tables in the database.

Answer

To filter data based on conditions.

Question 54

Which SQL command is used to modify existing data in a table?

Accepted Answer

UPDATE

Answer

DELETE

Answer

SELECT

Answer

INSERT

Question 55

What does the SQL keyword `DISTINCT` do?

Accepted Answer

Removes duplicate rows from the result set.

Answer

Sorts the result set in ascending order.

Answer

Adds new columns to the table.

Answer

Filters data based on specific criteria.

Question 56

Consider the SQL statement: `SELECT * FROM Products WHERE Price > 100 AND Category = 'Electronics';`. What will this statement retrieve?

Accepted Answer

All products from the 'Electronics' category with a price greater than 100.

Answer

All products with a price greater than 100, regardless of category.

Answer

All products from the 'Electronics' category regardless of price.

Question 57

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

Accepted Answer

To combine data from two or more tables based on a common column.

Answer

To update data in multiple tables simultaneously.

Answer

To create a new table from existing data.