Supabase: Join Auth Users Table - The Complete Guide

Hey guys! Ever found yourself wrestling with Supabase, trying to link your authentication users table with other data in your database? It’s a common challenge, and I’m here to walk you through it. We’re going to explore different methods to achieve this, ensuring you understand the why behind each step. So, let’s dive into the world of Supabase and get those tables talking!

Understanding the Basics: Supabase Auth and Tables

Before we get our hands dirty with joins, let’s quickly recap the essentials. Supabase provides a built-in authentication system that manages users, passwords, and all that jazz. When you create a new Supabase project, it automatically sets up an auth.users table. This table holds crucial information about your users, like their id (a UUID), email, and any metadata you might have added. Now, typically, you’ll want to extend this user information with additional details like profile data, preferences, or other application-specific attributes. This is where creating your own tables and linking them to the auth.users table becomes essential. You achieve this link using the user.id as a foreign key in your custom tables. By establishing this relationship, you can efficiently query and retrieve comprehensive user data by joining the auth.users table with your custom tables based on the matching user.id . This approach ensures data integrity and enables you to manage user-related information in a structured and scalable manner. This method is super useful because it keeps your core user data separate from the rest of your application’s data, which makes things cleaner and easier to manage. By joining these tables, you can pull all the info you need with a single query, avoiding multiple database calls and improving performance. Plus, it allows you to enforce relationships between your data, ensuring consistency and preventing orphaned records. So, understanding how to join the auth.users table with your own tables is a fundamental skill for building robust applications with Supabase. Trust me; mastering this will save you headaches down the road! Okay, with that foundation laid, let’s move on to the practical part: setting up your tables and performing the joins. We’ll start with the simplest scenario and then explore more advanced techniques as we go.

Method 1: Creating a User Profile Table and Performing a Join

In this method, we’ll create a separate profiles table to store additional user information. This is a very common pattern and a great starting point. First, you will need to design your profiles table. Think about the kind of information you want to store about each user. Common fields include full_name , avatar_url , bio , and any other profile-related details specific to your application. Make sure to include a user_id column in your profiles table. This column will act as the foreign key, linking each profile to the corresponding user in the auth.users table. Set up a foreign key constraint on the user_id column, referencing the id column in the auth.users table. This ensures data integrity and prevents orphaned profiles. Next, you can use SQL or the Supabase UI to create the profiles table. Here’s an example SQL statement:

CREATE TABLE profiles (
 user_id UUID PRIMARY KEY REFERENCES auth.users(id),
 full_name TEXT,
 avatar_url TEXT,
 bio TEXT
);

This SQL code creates a table named profiles with columns for user_id , full_name , avatar_url , and bio . The user_id column is set as the primary key and also references the id column in the auth.users table. Now you can perform a join between the auth.users table and the profiles table to retrieve user data along with their profile information. A simple SELECT statement with a JOIN clause will do the trick. Use the user_id column in both tables to establish the join condition. Here’s an example:

SELECT
 u.id AS user_id,
 u.email,
 p.full_name,
 p.avatar_url,
 p.bio
FROM
 auth.users u
INNER JOIN
 profiles p ON u.id = p.user_id;

This query selects the id and email from the auth.users table and the full_name , avatar_url , and bio from the profiles table. It joins the two tables based on the id column in the auth.users table and the user_id column in the profiles table. Now that you have your database set up, you can use the Supabase client library in your application code to query the joined data. Here’s an example using JavaScript:

const { data, error } = await supabase
 .from('auth.users')
 .select(`
 id,
 email,
 profiles ( full_name, avatar_url, bio )
 `)
 .single();

if (error) {
 console.error('Error fetching user data:', error);
} else {
 console.log('User data:', data);
}

This JavaScript code uses the Supabase client library to query the auth.users table and join it with the profiles table. It selects the id and email from the auth.users table and the full_name , avatar_url , and bio from the profiles table. The .single() method is used to retrieve a single user’s data. This method gives you a clean and organized way to manage user profiles, keeping your core user data separate from additional profile information.

Method 2: Using Row Level Security (RLS) with Joins

Row Level Security (RLS) is a powerful feature in PostgreSQL that allows you to control which rows users can access based on predefined policies. When combined with joins, RLS becomes incredibly useful for securing your data and ensuring that users can only access the information they are authorized to see. This is especially useful in multi-tenant applications . First, you’ll need to enable RLS on the tables you want to protect. In this case, we’ll focus on the profiles table we created in the previous method. You can enable RLS using the following SQL command:

ALTER TABLE profiles ENABLE ROW LEVEL SECURITY;

This command enables RLS on the profiles table. Next, you’ll need to create policies that define the conditions under which users can access rows in the profiles table. A common policy is to allow users to only access their own profile data. Here’s an example of such a policy:

”`sql CREATE POLICY