Relational Databases: Master Database Management with SQL

Question 1

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

Accepted Answer

ARRAY

Answer

INTEGER

Answer

VARCHAR

Answer

DATE

Question 2

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

Accepted Answer

SELECT

Answer

INSERT

Answer

UPDATE

Answer

DELETE

Question 3

What is the difference between the UNION and INTERSECT operators in SQL?

Accepted Answer

UNION combines rows from two or more tables, while INTERSECT finds only matching rows

Answer

INTERSECT combines rows from two or more tables, while UNION finds only matching rows

Answer

UNION removes duplicate rows, while INTERSECT keeps duplicate rows

Answer

UNION is used for selecting columns, while INTERSECT is used for selecting rows

Question 4

What is the primary purpose of an index in a relational database?

Accepted Answer

To improve query performance by quickly locating data

Answer

To enforce data integrity

Answer

To identify a unique row in a table

Answer

To prevent duplicate data entries

Question 5

Which feature characterizes a relational database model?

Accepted Answer

Data is organized into tables comprising rows and columns.

Answer

Data is organized hierarchically.

Answer

Data is not shared between tables.

Answer

Data is stored in a flat file.

Question 6

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

Accepted Answer

To uniquely identify each row.

Answer

To store the most crucial data in the table.

Answer

To establish connections between tables.

Answer

To optimize query execution speed.

Question 7

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

Accepted Answer

To filter the rows retrieved by the query.

Answer

To arrange the order of rows retrieved by the query.

Answer

To combine rows retrieved from multiple tables.

Answer

To group the rows retrieved by the query.

Question 8

Which of the following is not a relational database management system (RDBMS)?

Accepted Answer

Microsoft Excel

Answer

MySQL

Answer

Oracle

Answer

Microsoft Access

Question 9

What is the role of a foreign key in a relational database table?

Accepted Answer

To ensure referential integrity.

Answer

To link the table to another table.

Answer

To store additional data about a row.

Answer

To optimize query execution speed.

Question 10

What is the purpose of the JOIN statement in an SQL query?

Accepted Answer

To merge rows from multiple tables.

Answer

To filter the rows retrieved by the query.

Answer

To sort the rows retrieved by the query.

Answer

To group the rows retrieved by the query.

Question 11

What is the purpose of a transaction in a relational database system?

Accepted Answer

To ensure that a series of database operations are executed as a single unit.

Answer

To allow multiple users to access the database simultaneously.

Answer

To back up the database.

Answer

To restore the database from a backup.

Question 12

Which SQL command retrieves data from a database?

Accepted Answer

SELECT

Answer

INSERT

Answer

UPDATE

Answer

DELETE

Question 13

Which SQL data type should be used to store dates and times?

Accepted Answer

DATE

Answer

VARCHAR

Answer

INTEGER

Answer

BOOLEAN

Question 14

What is the main function of a foreign key in a relational database?

Accepted Answer

To establish a link between two tables

Answer

To ensure that data is not duplicated

Answer

To store additional data about a row

Answer

To uniquely identify each row in a table

Question 15

Which of the following is NOT an advantage of using a relational database?

Accepted Answer

Increased complexity

Answer

Data consistency

Answer

Flexibility

Answer

Performance

Question 16

Distinguish between a primary key and a unique key.

Accepted Answer

A unique key can have duplicate values, unlike a primary key

Answer

A primary key can have duplicate values, unlike a unique key

Answer

A primary key is always a foreign key, but a unique key is not

Answer

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

Question 17

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

Accepted Answer

STRING[]

Answer

INT

Answer

VARCHAR(50)

Answer

BIT

Question 18

Which SQL command is used to create a new table with specified columns and data types?

Accepted Answer

CREATE TABLE

Answer

ADD TABLE

Answer

MAKE TABLE

Answer

GENERATE TABLE

Question 19

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

Accepted Answer

To uniquely identify each row in a table

Answer

To enforce data integrity by preventing duplicate values

Answer

To improve the performance of data retrieval queries

Answer

To establish relationships between different tables

Question 20

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

Accepted Answer

An INNER JOIN returns only matching rows from both tables, while an OUTER JOIN returns all rows from one table and matching rows from the other.

Answer

An OUTER JOIN returns only non-matching rows from both tables, while an INNER JOIN returns all rows from one table and non-matching rows from the other.

Answer

An INNER JOIN combines rows based on equality, while an OUTER JOIN combines rows based on inequality.

Answer

There is no difference between INNER JOINs and OUTER JOINs.

Question 21

Which SQL command is primarily used to retrieve data from a table based on specified criteria?

Accepted Answer

SELECT

Answer

GET

Answer

FETCH

Answer

READ

Question 22

What is the main role of a foreign key in a relational database?

Accepted Answer

To establish and enforce relationships between tables, ensuring data integrity and consistency

Answer

To uniquely identify each row in a table, preventing duplicate entries

Answer

To improve the performance of data retrieval queries by optimizing join operations

Answer

To store additional information or attributes related to a row in a different table

Question 23

In a relational database, what is the primary function of a primary key?

Accepted Answer

Uniquely identifies each row in a table

Answer

Stores the most important data in the table

Answer

Establishes relationships between tables

Answer

Ensures the validity of all data in the table

Question 24

Which of the following is a syntactically correct SQL statement for creating a table named 'Customers'?

Accepted Answer

CREATE TABLE Customers (CustomerID INT, CustomerName STRING, Address STRING)

Answer

CREATE TABLE Customers {CustomerID INT, CustomerName STRING, Address STRING}

Answer

CREATE TABLE Customers (CustomerID: INT, CustomerName: STRING, Address: STRING)

Answer

CREATE TABLE Customers [CustomerID INT, CustomerName STRING, Address STRING]

Question 25

What is the key difference between a 'WHERE' clause and a 'HAVING' clause in SQL?

Accepted Answer

A 'WHERE' clause filters rows before grouping, while a 'HAVING' clause filters groups after grouping.

Answer

A 'HAVING' clause filters rows before grouping, while a 'WHERE' clause filters groups after grouping.

Answer

There is no difference between a 'WHERE' clause and a 'HAVING' clause.

Answer

A 'WHERE' clause filters columns, while a 'HAVING' clause filters rows.

Question 26

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

Accepted Answer

To uniquely identify each row in a table

Answer

To enforce referential integrity

Answer

To improve query performance

Answer

To store additional information about a row

Question 27

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

Accepted Answer

CREATE TABLE

Answer

SELECT

Answer

INSERT

Answer

UPDATE

Question 28

What is the key difference between a join and a subquery?

Accepted Answer

A join combines rows from multiple tables based on a common column, while a subquery is a nested query that returns a set of rows

Answer

A subquery is a nested query that returns a single value, while a join combines rows from multiple tables based on a common column

Answer

A join is a type of subquery

Answer

A subquery is a type of join

Question 29

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

Accepted Answer

=

Answer

!=

Answer

>

Answer

<

Question 30

What is the primary purpose of a transaction in a relational database?

Accepted Answer

To maintain data integrity

Answer

To improve query performance

Answer

To reduce data redundancy

Answer

To store metadata about a table

Question 31

Which SQL query retrieves data on customers who have placed multiple orders?

Accepted Answer

SELECT * FROM Customers WHERE OrderID IN (SELECT OrderID FROM Orders GROUP BY OrderID HAVING COUNT(*) > 1);

Answer

SELECT * FROM Customers WHERE OrderID > 1;

Answer

SELECT CustomerID FROM Orders GROUP BY CustomerID HAVING COUNT(*) > 1;

Answer

SELECT * FROM Customers, Orders WHERE Customers.CustomerID = Orders.CustomerID AND COUNT(*) > 1;

Question 32

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

Accepted Answer

CURRENCY

Answer

INTEGER

Answer

VARCHAR(255)

Answer

BOOLEAN

Question 33

Which of the following operators is used to test for equality between two values in SQL?

Accepted Answer

=

Answer

>

Answer

&&

Answer

LIKE

Question 34

What is the main purpose of an index in a relational database?

Accepted Answer

To speed up data retrieval

Answer

To enforce data integrity

Answer

To store frequently used data

Answer

To backup data

Question 35

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

Accepted Answer

To filter records based on a specified condition

Answer

To sort records in a specific order

Answer

To group records by a common value

Answer

To create a new table

Question 36

What is the purpose of a foreign key?

Accepted Answer

To establish a relationship between a field in one table and a field in another table

Answer

To make sure that data in a table is unique

Answer

To ensure that data in a table is not null

Answer

To help sort records in a table

Question 37

What is the difference between a row and a column in a relational database table?

Accepted Answer

A row contains data for a single record, while a column contains data for a specific field

Answer

A column contains data for a single record, while a row contains data for a specific field

Answer

A row and a column are the same thing

Answer

There is no difference between a row and a column

Question 38

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

Accepted Answer

To uniquely identify each row in the table and maintain data integrity.

Answer

To create an index for faster query performance.

Answer

To establish relationships between tables.

Answer

To store the most significant data in the table.

Question 39

Which of the following is a defining characteristic of a relational database model?

Accepted Answer

Data is organized into tables consisting of rows and columns

Answer

Data is stored in a hierarchical tree structure

Answer

Records are linked using pointers

Answer

The database follows a graph-based data model

Question 40

In SQL, which statement is used to retrieve all records from the 'Customers' table?

Accepted Answer

SELECT * FROM Customers

Answer

GET Customers

Answer

FETCH Customers

Answer

READ Customers

Question 41

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

Accepted Answer

To uniquely identify each record within a table

Answer

To enforce relationships between tables

Answer

To store additional information about a record

Answer

To improve query performance

Question 42

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

Accepted Answer

ARRAY

Answer

INT

Answer

CHAR

Answer

BOOLEAN

Question 43

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

Accepted Answer

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

Answer

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

Answer

INNER JOIN is used for one-to-many relationships, while OUTER JOIN is used for many-to-many relationships

Answer

There is no difference between INNER JOIN and OUTER JOIN

Question 44

Which attribute is a defining characteristic of relational databases?

Accepted Answer

Data is organized into structured tables

Answer

Data is accessed through a graphical interface

Answer

Data is represented as a network of nodes and edges

Answer

Data is stored as unstructured objects

Question 45

In Structured Query Language (SQL), which command is used to retrieve data from a database?

Accepted Answer

SELECT

Answer

DELETE

Answer

UPDATE

Answer

INSERT

Question 46

What is the primary function of a primary key in a relational database table?

Accepted Answer

To uniquely identify each record in the table

Answer

To specify the data type of each field

Answer

To maintain referential integrity between tables

Question 47

Which advantage is associated with utilizing foreign key constraints?

Accepted Answer

Preventing data inconsistencies by ensuring referential integrity

Answer

Enhancing database performance

Answer

Simplifying database schema design

Question 48

What is the purpose of applying a NOT NULL constraint to a column in a relational database?

Accepted Answer

To prohibit the insertion of null values into that column

Answer

To create an index on the column for faster data retrieval

Answer

To enforce referential integrity with other tables

Question 49

What is the main benefit of creating an index on a column in a relational database?

Accepted Answer

Accelerating data retrieval operations

Answer

Ensuring data integrity and consistency

Answer

Storing metadata about the database structure

Answer

Enforcing business rules and data validation

Question 50

Which database normalization form aims to eliminate data redundancy and anomalies, resulting in a well-structured and efficient database design?

Accepted Answer

Third Normal Form (3NF)

Answer

First Normal Form (1NF)

Answer

Second Normal Form (2NF)

Answer

Fourth Normal Form (4NF)

Question 51

Which concurrency control mechanism is commonly used in relational databases to prevent simultaneous access conflicts and ensure data integrity?

Accepted Answer

Locking

Answer

Timestamping

Answer

Versioning

Answer

Optimistic concurrency control