SQL Syntax and Structure: Master the Fundamentals of SQL

Question 1

Which data type is NOT supported by SQL?

Accepted Answer

Array

Answer

Integer (INT)

Answer

Variable-length character string (VARCHAR)

Answer

Logical value (BOOLEAN)

Question 2

Which SQL statement is used to establish a new table?

Accepted Answer

CREATE TABLE

Answer

SELECT

Answer

INSERT

Answer

UPDATE

Question 3

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

Accepted Answer

To select rows based on a specified condition

Answer

To arrange rows in ascending order

Answer

To group rows by a specified column

Answer

To add new rows to a table

Question 4

Which SQL function is used to determine the number of rows in a table?

Accepted Answer

COUNT()

Answer

SUM()

Answer

MIN()

Answer

MAX()

Question 5

What is the purpose of this SQL statement?
SELECT * FROM customers WHERE city = 'London';

Accepted Answer

Retrieve all data from the customers table where the city column matches 'London'

Answer

Modify all data in the customers table where the city column matches 'London'

Answer

Insert a new row into the customers table with the city column set to 'London'

Answer

Remove all data from the customers table where the city column matches 'London'

Question 6

What is the purpose of a foreign key in an SQL database?

Accepted Answer

To ensure data integrity between related tables

Answer

To create a unique index on a column

Answer

To define the primary key of a table

Answer

To group rows by a specified column

Question 7

Which keyword is used to create a new table in SQL?

Accepted Answer

CREATE TABLE

Answer

TABLE

Question 8

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

Accepted Answer

To identify each row uniquely

Answer

To enforce data integrity

Answer

To improve performance

Question 9

What is the difference between a WHERE clause and a HAVING clause?

Accepted Answer

WHERE filters rows, while HAVING filters groups of rows

Answer

HAVING filters rows, while WHERE filters groups of rows

Question 10

What is the purpose of a transaction in SQL?

Accepted Answer

To ensure data integrity

Answer

To improve performance

Question 11

How does SQL interact with a database management system (DBMS) to manipulate data?

Accepted Answer

SQL sends queries to the DBMS, which executes the queries and returns the modified data.

Answer

SQL creates tables in the DBMS, which then stores and manages the data in those tables.

Answer

SQL directly accesses and modifies the data stored in the DBMS.

Question 12

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

Accepted Answer

ARRAY

Answer

INTEGER

Answer

TEXT

Answer

BOOLEAN

Question 13

What is the main purpose of the 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 14

What is the purpose of the WHERE clause in SQL?

Accepted Answer

To filter data based on specified conditions

Answer

To sort data in a specific order

Answer

To group data by common values

Answer

To create a new table

Question 15

What is the main difference 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 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

Primary and foreign keys are the same thing.

Answer

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

Question 16

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

Accepted Answer

To sort data in a specified order

Answer

To filter data based on specified conditions

Answer

To group data by common values

Answer

To create a new table

Question 17

In SQL, which keyword is used to create a new table?

Accepted Answer

CREATE

Answer

NEW

Answer

ADD

Answer

DEFINE

Question 18

What's the main purpose of the GROUP BY clause in SQL?

Accepted Answer

Group rows by columns and aggregate data

Answer

Sort data in order

Answer

Remove duplicate rows

Question 19

The correct syntax to create a table named 'Students' with columns 'Name' (VARCHAR(255)), 'Age' (INT), and 'Grade' (INT) in SQL is:

Accepted Answer

CREATE TABLE Students (Name VARCHAR(255), Age INT, Grade INT);

Answer

CREATE TABLE 'Students' (Name VARCHAR(255), Age INT, Grade INT);

Answer

CREATE TABLE name Students (Name VARCHAR, Age INT, Grade FLOAT);

Answer

CREATE TABLE Students. (Name VARCHAR(255), Age INT, Grade DECIMAL);

Question 20

Which SQL data type is used to store dates and times?

Accepted Answer

DATETIME

Answer

VARCHAR

Answer

INT

Answer

FLOAT

Question 21

The operator used to compare two values for equality in SQL is:

Accepted Answer

=

Answer

==

Answer

>

Answer

<=

Question 22

The purpose of the 'WHERE' clause in an SQL statement is to:

Accepted Answer

Filter rows based on specified conditions

Answer

Order the results of a query

Answer

Group rows with similar values

Answer

Limit the number of rows returned

Question 23

Which SQL statement retrieves all records from the 'Students' table?

Accepted Answer

SELECT * FROM Students;

Answer

GET * FROM Students;

Answer

FETCH * FROM Students;

Answer

READ * FROM Students;

Question 24

A 'PRIMARY KEY' in an SQL table:

Accepted Answer

Uniquely identifies each row in a table

Answer

References a primary key in another table

Answer

References a foreign key in another table

Answer

Is a unique identifier for a group of rows

Question 25

The correct syntax to update the 'Age' column of a student named 'John' in the 'Students' table to 20 is:

Accepted Answer

UPDATE Students SET Age = 20 WHERE Name = 'John';

Answer

UPDATE 'Students' SET Age = 20 WHERE Name = John;

Answer

UPDATE Students. SET Age = '20' WHERE Name = 'John';

Answer

UPDATE Students (Age) SET 20 WHERE Name = John;

Question 26

An 'INDEX' in an SQL database is used to:

Accepted Answer

Improve the performance of data retrieval queries

Answer

Enforce data integrity and prevent duplicate values

Answer

Store data in a compressed format to save space

Answer

Provide a unique identifier for each row in a table

Question 27

The purpose of the 'JOIN' clause in an SQL statement is to:

Accepted Answer

Combine rows from two or more tables based on common values

Answer

Filter rows based on specified conditions

Answer

Order the results of a query

Answer

Group rows with similar values

Question 28

In SQL, how do you create a calculated column named `average_price` that calculates the average of the `price` column in a table called `sales`?

Accepted Answer

ALTER TABLE sales ADD COLUMN average_price AS AVG(price)

Answer

CREATE COLUMN average_price AS AVG(price) IN sales

Answer

ALTER sales ADD average_price AS AVG(price)

Answer

UPDATE sales SET average_price = AVG(price)

Question 29

In SQL, which keyword is used to create a primary key constraint, ensuring that each row in a table has a unique identifier?

Accepted Answer

PRIMARY KEY

Answer

UNIQUE

Answer

NOT NULL

Answer

DEFAULT

Question 30

Which action significantly enhances the execution speed of SQL queries?

Accepted Answer

Indexing frequently accessed columns

Answer

Increasing the number of columns in a table

Answer

Employing nested queries rather than multiple single queries

Answer

Omitting WHERE clauses

Question 31

In SQL, what's the main reason for using a PRIMARY KEY constraint?

Accepted Answer

To make sure each row in the table has a unique value for the chosen column(s).

Answer

To automatically create unique IDs for each row in the table.

Answer

To build an index on the chosen column(s) for quicker data retrieval.

Answer

To stop users from changing the data in the chosen column(s).

Question 32

Consider the following SQL query: ```SELECT * FROM students```. How can you modify this query to sort the 'students' table in ascending order by age?

Accepted Answer

Add `ORDER BY age` to the end of the query.

Answer

Add `ORDER BY age DESC` to the end of the query.

Answer

Change `SELECT *` to `SELECT age` at the beginning of the query.

Question 33

Which SQL query calculates the average age of students, grouped by their gender?

Accepted Answer

SELECT Gender, AVG(Age) FROM Students GROUP BY Gender

Answer

SELECT Gender, SUM(Age) FROM Students GROUP BY Gender

Answer

SELECT Gender, MAX(Age) FROM Students GROUP BY Gender

Answer

SELECT Age, AVG(Gender) FROM Students GROUP BY Age

Question 34

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

Accepted Answer

Object

Answer

Integer

Answer

Character

Answer

String

Question 35

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

Accepted Answer

To select specific rows from a table based on a condition

Answer

To group rows by a specified column

Answer

To update data in a table

Answer

To delete rows from a table

Question 36

Which operator is used to check if two values are not equal in an SQL statement?

Accepted Answer

!=

Answer

=

Answer

<

Answer

>

Question 37

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 update data in a table

Answer

To delete data from a table

Question 38

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

Accepted Answer

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

Answer

To group the results of a query

Answer

To filter the results of a query

Answer

To update the results of a query

Question 39

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

Accepted Answer

To uniquely identify each row in a table

Answer

To enforce relationships between tables

Answer

To store important data

Answer

To index data for faster retrieval

Question 40

Which type of SQL JOIN combines rows from two tables based on a common column value?

Accepted Answer

INNER JOIN

Answer

LEFT JOIN

Answer

RIGHT JOIN

Answer

FULL JOIN

Question 41

What is the benefit of using an index in an SQL database?

Accepted Answer

Improved query performance by reducing the time taken to retrieve data

Answer

Ensuring data integrity

Answer

Enforcing business rules

Answer

Providing data backup

Question 42

Which SQL statement is used to create a new table?

Accepted Answer

CREATE TABLE

Answer

DEFINE TABLE

Answer

GENERATE TABLE

Answer

ADD TABLE

Question 43

Which of the following is a valid SQL control flow statement that executes a block of code if a specified condition is met?

Accepted Answer

IF...THEN

Answer

WHILE...DO

Answer

FOR...EACH

Answer

SWITCH...CASE

Question 44

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

Accepted Answer

SELECT

Answer

EXTRACT

Answer

GET

Answer

FETCH

Question 45

Which SQL clause is used to specify a condition when retrieving data from a table?

Accepted Answer

WHERE

Answer

IF

Answer

ORDER BY

Answer

HAVING

Question 46

Which SQL keyword is used to group rows in a table before applying an aggregate function?

Accepted Answer

GROUP BY

Answer

CLUSTER

Answer

SORT BY

Answer

CLASSIFY

Question 47

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

Accepted Answer

DELETE

Answer

ERASE

Answer

REMOVE

Answer

PURGE

Question 48

Which SQL keyword is used to combine rows from two or more tables based on a shared column?

Accepted Answer

JOIN

Answer

LINK

Answer

CONNECT

Answer

ASSOCIATE

Question 49

Which of the following is the correct syntax for generating a table in SQL?

Accepted Answer

CREATE TABLE table_name (column_name data_type, ...);

Answer

CREATE TABLE table_name (column_name data_type);

Answer

TABLE table_name (column_name data_type, ...);

Answer

CREATE TABLE_ table_name (column_name data_type, ...);

Question 50

Which SQL operator represents logical OR?

Accepted Answer

OR

Answer

AND

Answer

NOT

Answer

XOR

Question 51

Which control flow statement in SQL is used to execute a block of code if a condition is met?

Accepted Answer

IF...THEN

Answer

IF...ELSE

Answer

ELSEIF

Answer

WHILE

Question 52

Which of the following is NOT a reserved keyword in SQL?

Accepted Answer

DATA

Answer

FROM

Answer

SELECT

Answer

WHERE

Question 53

Which SQL element defines a unique identifier for each row in a table?

Accepted Answer

Primary Key

Answer

Unique Key

Answer

Candidate Key

Answer

Foreign Key

Question 54

Which SQL clause groups rows based on a common value?

Accepted Answer

GROUP BY

Answer

ORDER BY

Answer

DISTINCT

Answer

HAVING