Module 1 · What is a database (and why SQL)?

What is a database, really?

🕑 4 min read

Goal of this lesson: You can explain in your own words what a database is and how it differs from a spreadsheet.

A database is a place where a program stores data in a neat, orderly way, so it can find that data again quickly and reliably later on. Almost everything you use day to day runs on one: your banking app knows your balance, a webshop knows which products exist and what you ordered, a booking system knows which seats are still free. All of that data lives in a database.

The best way to picture a database is as a collection of tables. A table looks like a sheet in a spreadsheet: it has columns (for example name, email, country) and rows (each row is one customer). One database usually holds several tables — say one for customers, one for products and one for orders — that together form a program's memory.

Why not just a spreadsheet?

A spreadsheet (like Excel or Google Sheets) is fine for a small list that one person updates now and then. But as soon as data gets serious, a spreadsheet hits its limits. A database is built for exactly those situations.

A database easily handles millions of rows, where a spreadsheet would grind to a halt. A hundred people can add and change data at the same time without overwriting each other's work. The database enforces the rules — for example that an email address may never be empty — so no mess creeps in. And you pull exactly the answer you want out of it with a single command, even from a mountain of data.

You give those commands in a language called SQL. Instead of scrolling through thousands of rows yourself, you ask the database a question — 'give me all customers from the Netherlands who bought something this month' — and get the answer back. That language is what you learn in this course.

SQL

SELECT name, email
FROM customers
WHERE country = 'NL';

Above you get an early look at what a question to a database looks like. You don't need to be able to write this yet — just notice how readable it is: 'pick the name and email columns from the customers table, but only where the country is NL'. That is the whole idea behind SQL: you describe *what* you want to know, and the database finds it for you.

Remember: A database stores data in tables (rows and columns), just like a spreadsheet — but built for large volumes, many users at once, strict rules and fast, precise questions. You ask those questions with SQL.

Try it yourself

Think of an app or website you use often (a webshop, a social network, your bank).
Write down which data you think it has to remember. Which tables would you expect? (Think: users, messages, orders, products.)
For each table, come up with a few columns. What does the app know about one user or one order?
Keep this list. Later in the course you will query exactly these kinds of tables, and even build them yourself.

Stuck?

Is a database the same as a server? No. A server is the computer; the database is the software that manages the data on it. They often run together, but they are different things.
Do I need to install anything now? Not yet. In this module you learn the concepts. In lesson 1.3 we point you to a free practice environment for when you want to type along.
I know Excel well — is that a disadvantage? Quite the opposite. Everything you know about rows, columns and filtering helps you here. SQL is the more powerful, precise version of that same idea.

Check yourself

In your own words, what is a database, and what does a table consist of?
Name two things a database does better than a spreadsheet.
What do you do with the SQL language?