No coding and no experience needed. In about eight minutes you will learn what a database is (with a library, an almirah, a book and a page), how a business becomes tables, and how our 55-table practice database, RetailMart, is organised.
Open in Present mode · Explore the database · Try the playground
Jo video mein bola, yahan nukte mein likha hai.
What I said in the video, written here as key points.
Ordered at 11 PM • At your door by 8 AM
Itni jaldi kaise? How is that even possible? The answer is data.
The idea: when you order something at night and it arrives in the morning, that is not magic. Every step of the journey is written down somewhere, as data. This video is a tour of a small, realistic version of that world. No coding and no experience needed.
Har cheez ka apna thikana. Everything has its place. A database keeps all the data neatly organised, like a library keeps its books. We will go deeper later.
Think of a library: a place that keeps thousands of books, neatly organised, so any book can be found. A computer keeps data the same way, in a database: the library is the database, and the books are the data. Books are kept in almirahs, one topic in each, and in SQL an almirah is a schema. Each book covers one topic, and a book is a table. Inside the book are pages, and each page is a row. We will go deeper into all of this later in the course.
Picture an Amazon warehouse with four floors. You order a microphone. The manager says "second floor, pick it up", it is packed, and a delivery person brings it to your home. You cannot walk in and grab it yourself (aap seedha andar ja ke utha nahi sakte). RetailMart records every one of those steps as a table:
| customer_id | first_name | last_name | tier |
|---|---|---|---|
| 1 | Meera | Naidu | Bronze |
| 2 | Lakshmi | Singh | Silver |
| 3 | Zoya | Lal | Bronze |
| 4 | Pallavi | Vyas | Silver |
| 5 | Jaspreet | Shetty | Bronze |
Wahi kitaab, ab asli data. The same book, now with real data. Each line is one customer, and one customer is one row.
This is the book you opened in the library, but with real data. The almirah is the customers schema, the book is the customers table, and every line is a row: one customer per row. RetailMart's customers table has 50,000 rows, and these are the first five.
A real business, not toy tables
Sounds like a lot? Ghabrana nahi hai. You will not memorise 55 tables. We start with six.
RetailMart has 16 schemas, 55 tables and about 24 lakh rows: 50,000 customers, 6,036 products, 200 stores, 1,50,000 orders and 3,75,202 order lines, from January 2024 to February 2026. Don't worry about memorising 55 tables. Start with six and look up the rest when you need them, like a library catalogue.
Bas itni si kahani hai. A customer places an order. An order has items. Each item is a product. That is the whole story.
Start with these six: customers.customers, products.products, sales.orders, sales.order_items, stores.stores and core.dim_region. Orders connect customers to what they bought, and order items connect each order to its products. Open the full dataset explorer for the real ER diagram and search across all 55 tables.
Dusre ka saaman mat chhedo. Don't disturb what isn't yours.
One rule: never change RetailMart's data. It is read-only. For your own experiments there is a separate database called practice, where you can create, break and fix as much as you like.
Chalo, pehli query. In plain words: show me everything from the customers table, just the first 10 rows.
The browser playground is only a taste. Real practice happens on your own laptop, and the next video puts this database there. The query is SELECT * FROM customers.customers LIMIT 10;, which means: show me everything from the customers table, just the first 10 rows.
Tell me in the comments. Milte hain agli video mein. Next: load the RetailMart database onto your laptop.