What is a database in SQL - Practice Questions & Exercises

Challenge - 5 Problems

🧠 Conceptual

intermediate

Understanding the core purpose of a database

Which of the following best describes the main purpose of a database?

A To create graphics and animations for websites

B To write and compile programming code

C To store and organize data so it can be easily accessed and managed

D To design user interfaces for mobile apps

💡 Hint

Think about what you do when you want to keep information safe and find it quickly later.

A database is a system designed to store data in an organized way, making it easy to access, manage, and update.

🧠 Conceptual

intermediate

Identifying database components

Which of these is NOT a typical component of a database system?

A Web browser for internet surfing

B Data storage

C User interface for data entry

D Database Management System (DBMS)

💡 Hint

Think about what parts help manage data versus what is used for browsing the internet.

A web browser is not part of a database system; it is used to access websites, not to manage or store data.

❓ query_result

advanced

Query result from a simple database table

Given a table Users with columns id and name, what is the result of this query?

SELECT name FROM Users WHERE id = 2;

SQL

CREATE TABLE Users (id INT, name VARCHAR(20));
INSERT INTO Users VALUES (1, 'Alice'), (2, 'Bob'), (3, 'Charlie');

A []

B [{'id': 2}]

C [{'name': 'Alice'}]

D [{'name': 'Bob'}]

💡 Hint

Look for the row where id equals 2 and return the name.

The query selects the name from the Users table where id is 2, which is 'Bob'.

📝 Syntax

advanced

Identify the syntax error in SQL query

Which option contains a syntax error in the SQL query?

SELECT * FROM Customers WHERE age > 30;

A SELECT * Customers WHERE age > 30;

B ;03 > ega EREHW sremotsuC MORF * TCELES

C SELECT * FROM Customers WHERE age > 30

D SELECT * FROM Customers WHERE age > 30;

💡 Hint

Check if the keyword FROM is used correctly.

Option A is missing the FROM keyword, causing a syntax error.

❓ optimization

expert

Optimizing a database query for performance

You have a large table Orders with millions of rows. Which query is likely to run faster?

Option 1: SELECT * FROM Orders WHERE order_date = '2023-01-01';
Option 2: SELECT * FROM Orders WHERE YEAR(order_date) = 2023 AND MONTH(order_date) = 1 AND DAY(order_date) = 1;

A Option 2 runs faster because it breaks the date into parts.

B Option 1 runs faster because it can use an index on order_date directly.

C Both run at the same speed because they filter the same data.

D Neither runs faster; a full table scan is always needed.

💡 Hint

Think about how indexes work with functions on columns.

Option 1 can use an index on order_date directly, making it faster. Option 2 applies functions to the column, preventing index use.