Run your first Supabase query — insert a row and read it back. Use when starting a new Supabase project, verifying your connection works, or learning the basic insert-then-select pattern with @supabase/supabase-js. Trigger with phrases like "supabase hello world", "first supabase query", "supabase quick start", "test supabase connection", "supabase insert and select".
Execute your first real Supabase query: create a todos table in the dashboard, insert a row with the JS client, and read it back. This validates that your project URL, anon key, and Row Level Security are configured correctly before you build anything else.
supabase-install-auth setup (project URL + anon key in .env)@supabase/supabase-js v2+ installed (npm install @supabase/supabase-js)todos TableOpen your Supabase dashboard SQL Editor and run:
-- Create a simple todos table
create table public.todos (
id bigint generated always as identity primary key,
task text not null,
is_complete boolean default false,
inserted_at timestamptz default now()
);
-- Enable Row Level Security (required for anon key access)
alter table public.todos enable row level security;
-- Allow anyone with the anon key to read and insert
-- (permissive for hello-world; lock down before production)
create policy "Allow public read" on public.todos
for select using (true);
create policy "Allow public insert" on public.todos
for insert with check (true);
Verify the table appears under Table Editor in the dashboard before continuing.
import { createClient } from '@supabase/supabase-js'
const supabase = createClient(
process.env.SUPABASE_URL!,
process.env.SUPABASE_ANON_KEY!
)
// Insert a row and return it with .select()
const { data, error } = await supabase
.from('todos')
.insert({ task: 'Hello from Supabase!' })
.select()
if (error) {
console.error('Insert failed:', error.message)
// e.g. "new row violates row-level security policy"
process.exit(1)
}
console.log('Inserted:', data)
// [{ id: 1, task: "Hello from Supabase!", is_complete: false, inserted_at: "2026-03-22T..." }]
Key detail: .insert() alone returns { data: null }. You must chain .select() to get the inserted row back.
// Select all rows from todos
const { data: todos, error: selectError } = await supabase
.from('todos')
.select('*')
if (selectError) {
console.error('Select failed:', selectError.message)
process.exit(1)
}
console.log('Todos:', todos)
// [{ id: 1, task: "Hello from Supabase!", is_complete: false, inserted_at: "2026-03-22T..." }]
// Verify the round-trip
if (todos && todos.length > 0) {
console.log('Round-trip verified — row exists in database')
} else {
console.error('No rows returned. Check RLS policies.')
}
Open the Table Editor in the Supabase dashboard to visually confirm the row is there.
todos table created with RLS enabled.select('*')| Error | Cause | Solution |
|---|---|---|
relation "public.todos" does not exist | Table not created | Run the Step 1 SQL in the dashboard SQL Editor |
new row violates row-level security policy | RLS blocks the insert | Add the permissive insert policy from Step 1 |
Invalid API key | Wrong anon key in .env | Copy from Settings > API in the dashboard |
FetchError: request to https://... failed | Wrong project URL | Verify SUPABASE_URL matches dashboard URL |
data is null after insert | Missing .select() chain | Add .select() after .insert() |
| Empty array returned from select | RLS blocks reads | Add the select policy from Step 1 |
import { createClient } from '@supabase/supabase-js'
const supabase = createClient(
process.env.SUPABASE_URL!,
process.env.SUPABASE_ANON_KEY!
)
async function helloSupabase() {
// Insert
const { data: inserted, error: insertErr } = await supabase
.from('todos')
.insert({ task: 'Hello from TypeScript!' })
.select()
.single()
if (insertErr) throw new Error(`Insert: ${insertErr.message}`)
console.log('Inserted:', inserted)
// Read back
const { data: rows, error: selectErr } = await supabase
.from('todos')
.select('*')
.order('inserted_at', { ascending: false })
.limit(5)
if (selectErr) throw new Error(`Select: ${selectErr.message}`)
console.log('Recent todos:', rows)
}
helloSupabase().catch(console.error)
from supabase import create_client
import os
supabase = create_client(
os.environ["SUPABASE_URL"],
os.environ["SUPABASE_ANON_KEY"]
)
# Insert a row
result = supabase.table("todos").insert({"task": "Hello from Python!"}).execute()
print("Inserted:", result.data)
# [{"id": 2, "task": "Hello from Python!", "is_complete": False, ...}]
# Read it back
result = supabase.table("todos").select("*").execute()
print("All todos:", result.data)
Install the Python client with: pip install supabase
Proceed to supabase-local-dev-loop for local development workflow with the Supabase CLI.