Explore database examples covering CRUD operations, relations, Row Level Security, triggers, functions, and advanced queries.Documentation Index
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CRUD Operations
Select Data
import { createClient } from '@supabase/supabase-js'
const supabase = createClient(url, key)
// Select all columns
const { data, error } = await supabase
.from('posts')
.select('*')
// Select specific columns
const { data } = await supabase
.from('posts')
.select('id, title, author_id')
// Select with filters
const { data } = await supabase
.from('posts')
.select('*')
.eq('author_id', userId)
.order('created_at', { ascending: false })
.limit(10)
// Select with text search
const { data } = await supabase
.from('posts')
.select('*')
.textSearch('title', 'supabase', {
type: 'websearch',
config: 'english',
})
// Select with range
const { data } = await supabase
.from('posts')
.select('*')
.range(0, 9) // Get first 10 rows
Insert Data
// Insert single row
const { data, error } = await supabase
.from('posts')
.insert({
title: 'Hello World',
content: 'This is my first post',
author_id: userId,
})
.select()
.single()
// Insert multiple rows
const { data, error } = await supabase
.from('posts')
.insert([
{ title: 'Post 1', content: 'Content 1' },
{ title: 'Post 2', content: 'Content 2' },
])
.select()
// Upsert (insert or update)
const { data, error } = await supabase
.from('posts')
.upsert({
id: 1,
title: 'Updated Title',
content: 'Updated content',
})
.select()
Update Data
// Update with filter
const { data, error } = await supabase
.from('posts')
.update({ title: 'New Title' })
.eq('id', postId)
.select()
// Update multiple rows
const { data, error } = await supabase
.from('posts')
.update({ status: 'published' })
.in('id', [1, 2, 3])
.select()
// Increment a value
const { data, error } = await supabase.rpc('increment_views', {
post_id: postId,
})
Delete Data
// Delete with filter
const { error } = await supabase
.from('posts')
.delete()
.eq('id', postId)
// Delete multiple rows
const { error } = await supabase
.from('posts')
.delete()
.in('id', [1, 2, 3])
// Delete all rows (be careful!)
const { error } = await supabase
.from('posts')
.delete()
.neq('id', 0) // This deletes everything
Relations and Joins
One-to-Many
// Get posts with author information
const { data } = await supabase
.from('posts')
.select(`
*,
author:profiles(
id,
username,
avatar_url
)
`)
// Get user with all their posts
const { data } = await supabase
.from('profiles')
.select(`
*,
posts(
id,
title,
created_at
)
`)
.eq('id', userId)
.single()
Many-to-Many
// Get posts with tags (through junction table)
const { data } = await supabase
.from('posts')
.select(`
*,
post_tags(
tags(
id,
name
)
)
`)
// Get tag with all posts
const { data } = await supabase
.from('tags')
.select(`
*,
post_tags(
posts(
id,
title
)
)
`)
.eq('id', tagId)
Nested Relations
// Get posts with author and comments
const { data } = await supabase
.from('posts')
.select(`
*,
author:profiles(*),
comments(
id,
content,
author:profiles(
username,
avatar_url
)
)
`)
Filtering
Comparison Operators
// Equal
const { data } = await supabase.from('posts').select().eq('status', 'published')
// Not equal
const { data } = await supabase.from('posts').select().neq('status', 'draft')
// Greater than
const { data } = await supabase.from('posts').select().gt('views', 1000)
// Greater than or equal
const { data } = await supabase.from('posts').select().gte('views', 1000)
// Less than
const { data } = await supabase.from('posts').select().lt('views', 1000)
// Less than or equal
const { data } = await supabase.from('posts').select().lte('views', 1000)
// In array
const { data } = await supabase.from('posts').select().in('status', ['published', 'archived'])
// Pattern matching
const { data } = await supabase.from('posts').select().like('title', '%supabase%')
// Case-insensitive pattern matching
const { data } = await supabase.from('posts').select().ilike('title', '%supabase%')
// Is null
const { data } = await supabase.from('posts').select().is('deleted_at', null)
Combining Filters
// AND (default)
const { data } = await supabase
.from('posts')
.select()
.eq('status', 'published')
.gt('views', 100)
// OR
const { data } = await supabase
.from('posts')
.select()
.or('status.eq.published,status.eq.archived')
// NOT
const { data } = await supabase
.from('posts')
.select()
.not('status', 'eq', 'draft')
Aggregation and Counting
// Count rows
const { count } = await supabase
.from('posts')
.select('*', { count: 'exact', head: true })
// Count with filter
const { count } = await supabase
.from('posts')
.select('*', { count: 'exact', head: true })
.eq('status', 'published')
// Sum, avg, min, max (using database functions)
const { data } = await supabase.rpc('get_post_stats', {
author_id: userId,
})
Row Level Security (RLS)
Enable RLS
-- Enable RLS on a table
alter table posts enable row level security;
Basic Policies
-- Allow users to read their own posts
create policy "Users can view their own posts"
on posts for select
using (auth.uid() = author_id);
-- Allow users to insert their own posts
create policy "Users can create posts"
on posts for insert
with check (auth.uid() = author_id);
-- Allow users to update their own posts
create policy "Users can update their own posts"
on posts for update
using (auth.uid() = author_id);
-- Allow users to delete their own posts
create policy "Users can delete their own posts"
on posts for delete
using (auth.uid() = author_id);
Advanced Policies
-- Public read, authenticated write
create policy "Public posts are viewable by everyone"
on posts for select
using (true);
create policy "Authenticated users can create posts"
on posts for insert
with check (auth.role() = 'authenticated');
-- Admins can do anything
create policy "Admins have full access"
on posts for all
using (
exists (
select 1 from profiles
where id = auth.uid()
and role = 'admin'
)
);
-- Collaborative editing
create policy "Collaborators can edit posts"
on posts for update
using (
auth.uid() = author_id
or exists (
select 1 from post_collaborators
where post_id = posts.id
and user_id = auth.uid()
)
);
Database Functions
Create Function
-- Increment views counter
create or replace function increment_views(post_id bigint)
returns void
language plpgsql
security definer
as $$
begin
update posts
set views = views + 1
where id = post_id;
end;
$$;
Call Function from Client
// Call function
const { data, error } = await supabase.rpc('increment_views', {
post_id: 123,
})
// Function that returns data
const { data, error } = await supabase.rpc('get_popular_posts', {
min_views: 1000,
})
Triggers
Auto-Update Timestamp
-- Create trigger function
create or replace function update_updated_at_column()
returns trigger
language plpgsql
as $$
begin
new.updated_at = now();
return new;
end;
$$;
-- Create trigger
create trigger update_posts_updated_at
before update on posts
for each row
execute function update_updated_at_column();
Auto-Create Related Records
-- Auto-create profile on user signup
create or replace function handle_new_user()
returns trigger
language plpgsql
security definer
as $$
begin
insert into public.profiles (id, username, avatar_url)
values (
new.id,
new.raw_user_meta_data->>'username',
new.raw_user_meta_data->>'avatar_url'
);
return new;
end;
$$;
create trigger on_auth_user_created
after insert on auth.users
for each row
execute function handle_new_user();
Full-Text Search
Set Up Full-Text Search
-- Add tsvector column
alter table posts
add column fts tsvector
generated always as (
to_tsvector('english', coalesce(title, '') || ' ' || coalesce(content, ''))
) stored;
-- Create index
create index posts_fts_idx on posts using gin(fts);
Search from Client
// Full-text search
const { data } = await supabase
.from('posts')
.select('*')
.textSearch('fts', 'supabase & postgres', {
type: 'websearch',
config: 'english',
})
Transactions
// Use a database function for transactions
const { data, error } = await supabase.rpc('transfer_funds', {
from_account: 123,
to_account: 456,
amount: 100,
})
// SQL function for transaction
/*
create or replace function transfer_funds(
from_account bigint,
to_account bigint,
amount numeric
)
returns void
language plpgsql
as $$
begin
-- Deduct from sender
update accounts
set balance = balance - amount
where id = from_account;
-- Add to receiver
update accounts
set balance = balance + amount
where id = to_account;
-- Insert transaction record
insert into transactions (from_account, to_account, amount)
values (from_account, to_account, amount);
end;
$$;
*/
Pagination
// Offset pagination
const pageSize = 10
const page = 2
const { data, error } = await supabase
.from('posts')
.select('*')
.range((page - 1) * pageSize, page * pageSize - 1)
// Cursor-based pagination
const { data, error } = await supabase
.from('posts')
.select('*')
.gt('created_at', lastPostTimestamp)
.order('created_at', { ascending: false })
.limit(10)
Real-time Subscriptions
// Subscribe to all changes
const channel = supabase
.channel('posts')
.on(
'postgres_changes',
{ event: '*', schema: 'public', table: 'posts' },
(payload) => {
console.log('Change received!', payload)
}
)
.subscribe()
// Subscribe to specific events
const channel = supabase
.channel('posts')
.on(
'postgres_changes',
{ event: 'INSERT', schema: 'public', table: 'posts' },
(payload) => {
console.log('New post:', payload.new)
}
)
.on(
'postgres_changes',
{ event: 'UPDATE', schema: 'public', table: 'posts' },
(payload) => {
console.log('Updated post:', payload.new)
}
)
.on(
'postgres_changes',
{ event: 'DELETE', schema: 'public', table: 'posts' },
(payload) => {
console.log('Deleted post:', payload.old)
}
)
.subscribe()
// Unsubscribe
supabase.removeChannel(channel)
Example Apps
Todo App
Complete CRUD operations with RLS
Employee Database
Advanced queries and relations
Blog Example
Full-text search and pagination
Next.js Slack Clone
Real-time subscriptions
Next Steps
Database Docs
Learn more about Postgres
Todo Tutorial
Build your first app
Row Level Security
Secure your data
Realtime Examples
Explore real-time patterns