Supabase Database

Supabase provides a full PostgreSQL database for storing your app’s data. Create tables, write queries, and let your data scale.

Prerequisites

Supabase connected
Basic understanding of your data needs

Creating Tables

In Supabase Dashboard

Go to Table Editor in sidebar
Click Create a new table
Name your table (e.g., tasks)
Add columns

Via Nativeline

You can also ask Nativeline:

Create a Supabase table for tasks with:
- id (auto-generated UUID)
- user_id (links to auth users)
- title (text, required)
- is_completed (boolean, default false)
- created_at (timestamp, auto)

Common Column Types

Type	Use For	Example
`uuid`	Unique IDs	Primary key, foreign keys
`text`	Strings	Names, descriptions
`int4/int8`	Numbers	Counts, quantities
`bool`	True/false	Is completed, is active
`timestamptz`	Dates/times	Created at, due date
`jsonb`	Complex data	Settings, metadata
`float8`	Decimals	Prices, coordinates

Example: Tasks Table

CREATE TABLE tasks (
  id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
  user_id UUID REFERENCES auth.users(id) NOT NULL,
  title TEXT NOT NULL,
  description TEXT,
  is_completed BOOLEAN DEFAULT false,
  due_date TIMESTAMPTZ,
  created_at TIMESTAMPTZ DEFAULT now(),
  updated_at TIMESTAMPTZ DEFAULT now()
);

Row Level Security (RLS)

Always enable RLS on tables with user data. Without it, anyone with your API key can read everything!

Enable RLS

Table Editor → Select table
Toggle “RLS” to enabled
Add policies

Common Policies

Users see only their data:

CREATE POLICY "Users view own tasks"
ON tasks FOR SELECT
USING (auth.uid() = user_id);

Users create own data:

CREATE POLICY "Users create own tasks"
ON tasks FOR INSERT
WITH CHECK (auth.uid() = user_id);

Users update own data:

CREATE POLICY "Users update own tasks"
ON tasks FOR UPDATE
USING (auth.uid() = user_id);

Users delete own data:

CREATE POLICY "Users delete own tasks"
ON tasks FOR DELETE
USING (auth.uid() = user_id);

CRUD Operations

Create (Insert)

Add a function to create a new task with the given title.
Save it to Supabase with the current user's ID.

Read (Select)

Load all tasks for the current user from Supabase.
Order them by created_at, newest first.

Update

Add a function to mark a task as complete.
Update the is_completed field in Supabase.

Delete

Add a function to delete a task from Supabase.
Show confirmation before deleting.

Querying Data

Basic Queries

// All tasks for current user (handled by RLS)
let tasks = try await supabase
  .from("tasks")
  .select()
  .execute()

// Filter by completion status
let incomplete = try await supabase
  .from("tasks")
  .select()
  .eq("is_completed", value: false)
  .execute()

// Order by date
let ordered = try await supabase
  .from("tasks")
  .select()
  .order("due_date", ascending: true)
  .execute()

Filtering Options

Method	Use	Example
`.eq()`	Equals	`eq("status", "active")`
`.neq()`	Not equals	`neq("status", "deleted")`
`.gt()`	Greater than	`gt("price", 100)`
`.lt()`	Less than	`lt("age", 30)`
`.gte()`	Greater or equal	`gte("rating", 4)`
`.like()`	Pattern match	`like("name", "%John%")`
`.in()`	In array	`in("status", ["active", "pending"])`
`.is()`	Is null/bool	`is("deleted_at", nil)`

Relationships

One-to-Many

Tasks belong to a category:

CREATE TABLE categories (
  id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
  user_id UUID REFERENCES auth.users(id),
  name TEXT NOT NULL
);

CREATE TABLE tasks (
  ...
  category_id UUID REFERENCES categories(id),
  ...
);

Querying with Relationships

// Get tasks with category names
let tasks = try await supabase
  .from("tasks")
  .select("*, categories(name)")
  .execute()

Handling Errors

Common Database Errors

Error	Cause	Solution
RLS policy violation	No matching policy	Check your policies
Foreign key violation	Referenced row missing	Ensure referenced data exists
Not null violation	Required field empty	Provide all required fields
Unique violation	Duplicate value	Check for existing records

Error Handling in App

Handle database errors gracefully:
- Show user-friendly error messages
- Log detailed errors for debugging
- Retry on network errors

Performance Tips

Add indexes for frequent queries

If you often query by a column (like user_id), add an index:

CREATE INDEX tasks_user_id_idx ON tasks(user_id);

Select only needed columns

Instead of select("*"), specify columns:

.select("id, title, is_completed")

Use pagination for large datasets

.range(from: 0, to: 19) // First 20 items

Cache locally for speed

Store frequently-accessed data locally and sync with Supabase.

Testing Database Operations

In Supabase Dashboard

Table Editor → Select table
View, add, edit, delete rows manually
Great for testing and debugging

Via SQL Editor

SQL Editor in Supabase sidebar
Write and run queries directly
Test policies and queries

Next Steps

Storage

Upload files and images

Realtime

Live data updates

​Supabase Database

​Prerequisites

​Creating Tables

​In Supabase Dashboard

​Via Nativeline

​Common Column Types

​Example: Tasks Table

​Row Level Security (RLS)

​Enable RLS

​Common Policies

​CRUD Operations

​Create (Insert)

​Read (Select)

​Update

​Delete

​Querying Data

​Basic Queries

​Filtering Options

​Relationships

​One-to-Many

​Querying with Relationships

​Handling Errors

​Common Database Errors

​Error Handling in App

​Performance Tips

​Testing Database Operations

​In Supabase Dashboard

​Via SQL Editor

​Next Steps

Storage

Realtime

Supabase Database

Prerequisites

Creating Tables

In Supabase Dashboard

Via Nativeline

Common Column Types

Example: Tasks Table

Row Level Security (RLS)

Enable RLS

Common Policies

CRUD Operations

Create (Insert)

Read (Select)

Update

Delete

Querying Data

Basic Queries

Filtering Options

Relationships

One-to-Many

Querying with Relationships

Handling Errors

Common Database Errors

Error Handling in App

Performance Tips

Testing Database Operations

In Supabase Dashboard

Via SQL Editor

Next Steps