# Generated Types, Seeding and Environments — Supabase

Source: https://www.skillbyai.com/en/supabase/w-types

> Type-safe queries and repeatable data.

## Types from the schema

`supabase gen types typescript` reads your database schema and writes a `Database` type; passing it to `createClient<Database>()` gives typed rows, inserts and RPC arguments. Regenerate after every migration, ideally in CI. `supabase/seed.sql` fills the local database with test data on `db reset`. Keep separate projects (or Supabase **branching**, which creates preview environments from Git branches on supported plans) for development, staging and production; check the docs for current branching options.

## Generating and using types

CLI plus TypeScript.

```typescript
// shell:
//   supabase gen types typescript --local > src/lib/database.types.ts
//   supabase gen types typescript --project-id your-project-ref > src/lib/database.types.ts

import { createClient } from '@supabase/supabase-js'
import type { Database } from './database.types'

const supabase = createClient<Database>(url, anonKey)

// title is typed as string, done as boolean
const { data } = await supabase.from('tasks').select('id, title, done')

type Task = Database['public']['Tables']['tasks']['Row']
```

## Fail CI when types are stale

Generate types in CI and compare with the committed file; a diff means someone changed the schema without updating types.

**Quiz:** What does passing the generated Database type to createClient give you?

- [ ] Automatic RLS policies
- [x] Typed rows, inserts and RPC arguments
- [ ] Faster queries at runtime
- [ ] Encrypted columns

*Answer:* Typed rows, inserts and RPC arguments. Types catch column and table typos at compile time.