Master SQL Data Query: Enhance Your Database Skills

Question 1

In SQL, which statement retrieves all rows from a specified table?

Accepted Answer

SELECT * FROM [Table_Name]

Answer

SELECT FROM [Table_Name]

Answer

SELECT ALL FROM [Table_Name]

Answer

SELECT ROWS FROM [Table_Name]

Question 2

Which clause groups rows based on common values in SQL?

Accepted Answer

GROUP BY

Answer

HAVING

Answer

ORDER BY

Answer

JOIN

Question 3

Which SQL function calculates the sum of values in a specified column?

Accepted Answer

SUM

Answer

COUNT

Answer

AVG

Answer

MAX

Question 4

Which join type connects two SQL tables based on a common column?

Accepted Answer

INNER JOIN

Answer

LEFT JOIN

Answer

RIGHT JOIN

Answer

FULL JOIN

Question 5

Which clause arranges the results of a SQL query in a specific order?

Accepted Answer

ORDER BY

Answer

SORT BY

Answer

GROUP BY

Answer

LIMIT BY

Question 6

Which SQL keyword limits the number of rows returned in a query?

Accepted Answer

LIMIT

Answer

OFFSET

Answer

TOP

Answer

FIRST

Question 7

Which clause eliminates duplicate rows from a SQL query's results?

Accepted Answer

DISTINCT

Answer

UNIQUE

Answer

GROUP BY

Answer

ORDER BY

Question 8

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

Accepted Answer

To filter rows based on a condition

Answer

To group rows with similar values

Answer

To order rows in a specific sequence

Answer

To create a new table

Question 9

What is the function of the DISTINCT keyword in a SQL query?

Accepted Answer

To remove duplicate rows from the result

Answer

To sort the results in ascending order

Answer

To group rows with similar values

Answer

To limit the number of rows returned

Question 10

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

Accepted Answer

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

Answer

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

Answer

INNER JOIN is faster than OUTER JOIN

Answer

There is no difference between INNER JOIN and OUTER JOIN

Question 11

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

Accepted Answer

UPDATE

Answer

INSERT

Answer

DELETE

Answer

SELECT

Question 12

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

Accepted Answer

To uniquely identify each row in the table

Answer

To enforce data integrity

Answer

To improve query performance

Answer

To store additional information about each row

Question 13

Which SQL statement is used to create a new table?

Accepted Answer

CREATE TABLE

Answer

ALTER TABLE

Answer

DROP TABLE

Answer

INSERT INTO

Question 14

What is the role of the ORDER BY clause in a SQL query?

Accepted Answer

To sort the results in a specific sequence

Answer

To filter rows based on a condition

Answer

To group rows with similar values

Answer

To limit the number of rows returned

Question 15

In an SQL database, which data type is appropriate for storing a person's name?

Accepted Answer

VARCHAR

Answer

INT

Answer

FLOAT

Answer

DATE

Question 16

To combine data from two tables based on matching values in multiple columns, which SQL join type is used?

Accepted Answer

INNER JOIN

Answer

LEFT JOIN

Answer

FULL OUTER JOIN

Question 17

In SQL, which clause is used to filter groups of data based on specific conditions?

Accepted Answer

HAVING

Answer

WHERE

Answer

SORT BY

Answer

GROUP BY

Question 18

Which of the following is a valid SELECT statement that retrieves all rows and columns from the 'users' table where the 'name' column equals 'John'?

Accepted Answer

SELECT * FROM users WHERE name = 'John';

Answer

SELECT name, age FROM users;

Answer

SELECT * FROM users ORDER BY age;

Answer

SELECT COUNT(*) FROM users;

Question 19

Which logical operator is used to filter rows based on a condition where both operands must be true?

Accepted Answer

AND

Answer

OR

Answer

NOT

Answer

BETWEEN

Question 20

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

Accepted Answer

To group rows having the same value for a specified column, allowing for aggregate functions to be applied

Answer

To sort rows based on a specified column value

Answer

To filter rows based on a specified column value

Answer

To count the number of rows in a table

Question 21

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

Accepted Answer

To sort the result set in ascending or descending order based on the specified column

Answer

To group rows based on a specified column value

Answer

To filter rows based on a specified column value

Answer

To count the number of rows in a table

Question 22

Explain the primary difference between a primary key and a foreign key in an SQL table.

Accepted Answer

A primary key uniquely identifies each row in a table, while a foreign key establishes a relationship with another table by referencing its primary key

Answer

A foreign key uniquely identifies each row in a table, while a primary key establishes a relationship with another table by referencing its foreign key

Answer

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

Answer

A primary key can be null, while a foreign key cannot

Question 23

In SQL, which keyword is used to retrieve data from a database table?

Accepted Answer

SELECT

Answer

INSERT

Answer

UPDATE

Answer

DELETE

Question 24

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

Accepted Answer

To filter the data returned based on specified criteria

Answer

To specify the table to query

Answer

To sort the data returned in a specific order

Answer

To group the data returned by one or more columns

Question 25

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

Accepted Answer

To retrieve data in a specific order based on one or more columns

Answer

To filter the data returned based on specified criteria

Answer

To group the data returned by one or more columns

Answer

To aggregate the data returned by performing calculations

Question 26

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

Accepted Answer

To group the data returned by one or more columns and perform aggregate calculations

Answer

To filter the data returned based on specified criteria

Answer

To sort the data returned in a specific order

Answer

To retrieve data in a specific order based on one or more columns

Question 27

Which DQL clause is used to retrieve only the columns you specify from a table?

Accepted Answer

SELECT

Answer

WHERE

Answer

ORDER BY

Answer

GROUP BY

Question 28

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

Accepted Answer

SELECT

Answer

INSERT

Answer

UPDATE

Answer

DELETE

Question 29

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

Accepted Answer

To filter data based on specified conditions

Answer

To sort data in ascending order

Answer

To group data by common values

Answer

To delete rows from a table

Question 30

What is the key difference between the 'AND' and 'OR' operators in SQL?

Accepted Answer

'AND' returns rows that satisfy all specified conditions, while 'OR' returns rows that satisfy any specified condition

Answer

'AND' returns rows that satisfy any specified condition, while 'OR' returns rows that satisfy all specified conditions

Answer

They both perform the same function, there is no difference

Answer

They cannot be used together in the same query

Question 31

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

Accepted Answer

MAX()

Answer

MIN()

Answer

AVG()

Answer

SUM()

Question 32

How can you sort the results of a SQL query in descending order?

Accepted Answer

ORDER BY DESC

Answer

USING DESC

Answer

SORT DESC

Answer

DESCENDING

Question 33

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

Accepted Answer

ARRAY

Answer

VARCHAR

Answer

INTEGER

Answer

BOOLEAN

Question 34

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

Accepted Answer

To uniquely identify each row in the table

Answer

To store additional information about each row

Answer

To enforce data integrity

Answer

To speed up query performance

Question 35

How does the CASE statement facilitate conditional evaluation and dynamic value assignment in SQL?

Accepted Answer

It allows conditional assignment of different values to a column based on specified conditions.

Answer

It simplifies data aggregation by grouping related values.

Answer

It sorts data in ascending or descending order based on a specified column.

Answer

It removes duplicate rows from a table.

Question 36

In SQL, which clause allows you to filter data based on specific conditions?

Accepted Answer

WHERE

Answer

SELECT

Answer

ORDER BY

Answer

GROUP BY

Question 37

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

Accepted Answer

To sort rows of data in a specific order

Answer

To group rows of data by a specified column

Answer

To filter rows of data based on a condition

Answer

To combine multiple rows of data into a single row

Question 38

What is the purpose of the following SQL statement: SELECT * FROM Customers WHERE Country = 'UK';

Accepted Answer

Retrieves all data from the Customers table where the Country column equals 'UK'

Answer

Updates all customers in the UK with a new address

Answer

Deletes all customers in the UK from the table

Answer

Creates a new table called 'UKCustomers'

Question 39

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

Accepted Answer

AVG()

Answer

SUM()

Answer

MAX()

Answer

MIN()

Question 40

What is the 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 or both tables.

Answer

An INNER JOIN returns all rows from both tables, while an OUTER JOIN returns only matching rows.

Answer

An INNER JOIN creates a new table, while an OUTER JOIN modifies the existing tables.

Answer

There is no difference between an INNER JOIN and an OUTER JOIN.

Question 41

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

Accepted Answer

To ensure each row in a table has a unique identifier

Answer

To create a foreign key relationship between two tables

Answer

To group data by a specified column

Answer

To sort data in ascending or descending order

Question 42

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

Accepted Answer

DATETIME

Answer

INT

Answer

VARCHAR

Answer

BOOLEAN

Question 43

What is the purpose of a foreign key in SQL?

Accepted Answer

To enforce data integrity by referencing a primary key

Answer

To establish a relationship between two tables

Answer

To create a unique index on a column

Answer

To store additional information about a row

Question 44

In SQL, which syntax checks if a column value matches any value in a given set using the IN operator?

Accepted Answer

SELECT * FROM table_name WHERE column_name IN (value1, value2, value3)

Answer

SELECT * FROM table_name WHERE column_name = (value1, value2, value3)

Answer

SELECT * FROM table_name WHERE column_name BETWEEN value1 AND value3

Answer

SELECT * FROM table_name WHERE column_name LIKE (value1, value2, value3)

Question 45

In SQL, which operator is used to select rows where a specified column's value is between two specified values?

Accepted Answer

BETWEEN

Answer

IN

Answer

LIKE

Answer

ALL

Question 46

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

Accepted Answer

SELECT

Answer

SHOW

Answer

GET

Answer

FETCH

Question 47

What keyword is used to add a condition to filter data in a SELECT statement?

Accepted Answer

WHERE

Answer

OR

Answer

THEN

Answer

IF

Question 48

Which symbol represents the 'not equal to' comparison operator in SQL?

Accepted Answer

<>

Answer

>

Answer

=

Answer

<

Question 49

Which function counts the number of rows in a table?

Accepted Answer

COUNT()

Answer

MIN()

Answer

SUM()

Answer

AVG()

Question 50

What keyword groups rows based on a specific column in a SELECT statement?

Accepted Answer

GROUP BY

Answer

DISTINCT

Answer

HAVING

Answer

ORDER BY

Question 51

What is the purpose of the ORDER BY clause in a SELECT statement?

Accepted Answer

To arrange the retrieved data in ascending or descending order.

Answer

To group the retrieved data by a specific column.

Answer

To filter the retrieved data based on a condition.

Question 52

What is the key difference between an inner join and an outer join?

Accepted Answer

An inner join only shows matching rows from both tables, while an outer join includes all rows from one or both tables.

Answer

An inner join shows all rows from both tables, while an outer join only shows matching rows.

Question 53

What is the main purpose of using subqueries in SQL?

Accepted Answer

To place one or more queries within another query.

Answer

To create a new table from query results.

Answer

To modify data based on query results.

Answer

To group data based on query results.