First questions to the data · Lesson 1 of 20

What are SQL and databases?

Tables, rows and columns, and your first query.

7 minutes2 games

Every app you use holds data: users, orders, messages. A database stores that data in an organized way, so you can search and change it quickly even with millions of rows.

The most common kind is the relational database: data is split into tables. Each table has fixed columns, and each row is one thing: one student, one course.

id	name	city	xp
1	Laila	Cairo	320
2	Karim	Alexandria	150
3	Omar	Cairo	90
…	…	…	…

The students table: each row is a student, each column a fact about them.

SQL (said "sequel" or "S-Q-L") is the language you use to talk to a database. You say what you want and the database decides how to get it. That's a declarative style, unlike JavaScript and Python where you write the steps yourself.

The first and most important command is SELECT: "give me". The star * means every column. Press Run:

SQL

SELECT * FROM students;

Quick question

In the students table, what does one row represent?

Exercise

There's another table called courses. Write a query that shows all of its columns and rows.

Expected result:

id | title | track | price | hours
1 | HTML & CSS | web | 0 | 12
2 | JavaScript | web | 450 | 30
3 | Python | data | 400 | 28
4 | SQL | data | 300 | 16
5 | React | web | 600 | 24
6 | C++ | systems | 500 | 36

SQL

-- Write your query here

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SQL