What's a Database? Getting Started with Supabase

Why Do You Need a Database?

Everything you’ve built so far disappears when the browser closes.

Sure, localStorage keeps data in your browser, but open a different device and it’s gone. Other users’ data? Totally inaccessible.

A database stores everyone’s data on a central server.

Analogy: localStorage is your desk drawer — only you can open it. A database is a library — organized, shared, and accessible from anywhere.

What’s Supabase?

A free database service. Think of it as a developer’s spreadsheet in the cloud.

Spreadsheet	Supabase
Sheet	Table
Row	Record (one entry)
Column	Column (name, email, etc.)
Saved locally	Saved in the cloud

The difference? A spreadsheet lives on your computer. Supabase is on the internet, so your app can read and write data in real time.

Hands-On: 5-Minute Setup

Step 1: Sign Up

supabase.com → log in with GitHub. Free.

Step 2: Create a Project

“New Project” → name it → set a password → pick a region (choose the closest one) → Create.

Wait about 2 minutes for it to spin up.

Step 3: Create a Table

Let’s say you’re building a to-do app:

CREATE TABLE todos (
  id uuid DEFAULT gen_random_uuid() PRIMARY KEY,
  title text NOT NULL,
  done boolean DEFAULT false,
  created_at timestamp DEFAULT now()
);

Translation:

• id: Unique identifier for each to-do (auto-generated)
• title: The task content (“Do math homework”)
• done: Completed or not (true/false)
• created_at: When it was created (auto-recorded)

Paste this in Supabase’s “SQL Editor” and hit Run. Table created.

Step 4: Connect from Your App

import { createClient } from '@supabase/supabase-js'

const supabase = createClient(
  'https://xxx.supabase.co',  // Project URL
  'eyJhbGciOi...'             // Public key (anon key)
)

Find both values in Supabase dashboard → Settings → API.

Step 5: Read and Write Data

// Add a to-do
await supabase.from('todos').insert({ title: 'Do homework' })

// Get all to-dos
const { data } = await supabase.from('todos').select('*')

// Mark as done
await supabase.from('todos').update({ done: true }).eq('id', '...')

// Delete
await supabase.from('todos').delete().eq('id', '...')

It reads like English:

• “From todos, insert a row with title ‘Do homework’”
• “From todos, select everything”

RLS: Row Level Security

RLS = rules for who can see what data.

Example: “Users can only see their own to-dos”

ALTER TABLE todos ENABLE ROW LEVEL SECURITY;

CREATE POLICY "users see own todos" ON todos
  FOR SELECT USING (auth.uid() = user_id);

With this, User A can never see User B’s data. It’s enforced at the database level — even a hacker can’t bypass it.

Free Tier Limits

Item	Limit
Database storage	500 MB
File storage	1 GB
API requests	Unlimited
Projects	2

More than enough for personal projects.

When to Use What

Situation	Choice
Solo app, small data	localStorage
Multi-device, multi-user	Supabase
User login needed	Supabase Auth
File uploads (images, etc.)	Supabase Storage

What’s Next?

These 6 guides cover the fundamentals:

1. AI can build your app
2. Git for saving your work
3. Vercel for deployment
4. Custom domains
5. Security basics
6. Databases with Supabase

Now go build something. When you get stuck, ask your AI and revisit these guides. You don’t need to understand everything upfront — you learn by building.