Data Fundamentals

Before we store any information in Supabase, we need to understand how data is organized in Postgres. Supabase uses Postgres as its database, which means data is arranged in a structured and predictable way. This helps keep your app organized, consistent, and easy to query.

The core ideas are simple: you create tables to hold related data, and each table has rows (records) and columns (fields). Once you understand that pattern, you can model almost anything.

Tables, rows, and columns

A table is like a spreadsheet. It has:

• Columns: the fields that define what kind of data the table stores
• Rows: the individual entries in the table

Imagine a table for storing notes:

| id | content          | created_at           |
|----|------------------|----------------------|
| 1  | Buy groceries    | 2025-01-10 14:22:11  |
| 2  | Call the dentist | 2025-01-10 15:08:54  |

• Each row is a single note.
• Each column represents one piece of information about the note.

Data types

Every column has a data type. This describes the kind of value that can be stored there.

Some common data types:

| Data type   | Example value    | Meaning                       |
| ----------- | ---------------- | ----------------------------- |
| text        | Hello world      | A string of characters        |
| integer     | 42               | A number without decimals     |
| boolean     | true             | Yes/no or on/off values       |
| timestamptz | 2025-01-10 14:22 | Date and time (with timezone) |
| json        | {"name": "John"} | A JSON object                 |

Choosing correct types makes your data easier to work with and protects you from unexpected values.

Primary keys

Most tables include a primary key. This is a column that uniquely identifies each row. In many Supabase projects, this column is named id and uses a type called uuid, which automatically generates a unique value.

You create this column in the table definition like this:

id uuid primary key default gen_random_uuid()

You generally don't need to think about it after setting it up. It simply gives each record a stable identity.

Relationships between tables

You can link tables together using foreign keys. This is how you express things like:

• A user has many notes
• A project has many tasks
• A team has many members

For example:

| id | user_id                              | content          | created_at           |
|----|--------------------------------------|------------------|----------------------|
| 1  | 9f1b1c94-3e7b-4d6a-9fa7-1e2a3c4ba987 | Buy groceries    | 2025-01-10 14:22:11  |
| 2  | 9f1b1c94-3e7b-4d6a-9fa7-1e2a3c4ba987 | Call the dentist | 2025-01-10 15:08:54  |

Here, user_id refers to a row in a users table. This means the note belongs to that user, and we can see that this user has two notes.

Relationships let you organize data without repeating information.

Why relational data is useful in practice

Relational data is really useful in practice because it allows you to:

• Keep data valid with constraints

  Example: no duplicate emails.

• Link records safely with foreign keys

  Example: delete a user and their notes in one action.

• Express real permissions with RLS

  Example: users can read their own notes; admins can read all.

• Query exactly what you need with table joins

  Example: fetch notes with the author's email.

What we learned

A database in Supabase is made up of tables. Each table has:

• columns (which describe the type of information stored)
• rows (the individual pieces of data in that table)

You can relate tables to each other using foreign keys. This lets you model real situations, such as:

• a user has many notes
• a team has many members
• a project has many tasks

Thinking in tables, rows, and relationships is the foundation of working with data in Supabase.