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Generate database seed scripts with realistic sample data. Reads Drizzle schemas or SQL migrations, respects foreign key ordering, produces idempotent TypeScript or SQL seed files. Handles D1 batch limits, unique constraints, and domain-appropriate data. Use when populating dev/demo/test databases. Triggers: 'seed database', 'seed data', 'sample data', 'populate database', 'db seed', 'test data', 'demo data', 'generate fixtures'.
npx skill4agent add jezweb/claude-skills db-seed| Source | Location pattern |
|---|---|
| Drizzle schema | |
| D1 migrations | |
| Raw SQL | |
| Prisma | |
| Parameter | Options | Default |
|---|---|---|
| Purpose | dev, demo, testing | dev |
| Volume | small (5-10 rows/table), medium (20-50), large (100+) | small |
| Domain context | "e-commerce store", "SaaS app", "blog", etc. | Infer from schema |
| Output format | TypeScript (Drizzle), raw SQL, or both | Match project's ORM |
1. users (no dependencies)
2. categories (no dependencies)
3. posts (depends on users, categories)
4. comments (depends on users, posts)
5. tags (no dependencies)
6. post_tags (depends on posts, tags)const firstNames = ['Sarah', 'James', 'Priya', 'Mohammed', 'Emma', 'Wei', 'Carlos', 'Aisha'];
const lastNames = ['Chen', 'Smith', 'Patel', 'Garcia', 'Kim', 'O\'Brien', 'Nguyen', 'Wilson'];sarah.chen@example.comexample.comconst randomDate = (daysBack: number) => {
const d = new Date();
d.setDate(d.getDate() - Math.floor(Math.random() * daysBack));
return d.toISOString();
};crypto.randomUUID()function seededRandom(seed: number) {
return () => {
seed = (seed * 16807) % 2147483647;
return (seed - 1) / 2147483646;
};
}
const rand = seededRandom(42); // Same seed = same data every time(rand() * 900 + 100).toFixed(2)// scripts/seed.ts
import { drizzle } from 'drizzle-orm/d1';
import * as schema from '../src/db/schema';
export async function seed(db: ReturnType<typeof drizzle>) {
console.log('Seeding database...');
// Clear existing data (reverse dependency order)
await db.delete(schema.comments);
await db.delete(schema.posts);
await db.delete(schema.users);
// Insert users
const users = [
{ id: crypto.randomUUID(), name: 'Sarah Chen', email: 'sarah@example.com', ... },
// ...
];
// D1 batch limit: 10 rows per INSERT
for (let i = 0; i < users.length; i += 10) {
await db.insert(schema.users).values(users.slice(i, i + 10));
}
// Insert posts (references users)
const posts = [
{ id: crypto.randomUUID(), userId: users[0].id, title: '...', ... },
// ...
];
for (let i = 0; i < posts.length; i += 10) {
await db.insert(schema.posts).values(posts.slice(i, i + 10));
}
console.log(`Seeded: ${users.length} users, ${posts.length} posts`);
}npx tsx scripts/seed.tsapp.post('/api/seed', async (c) => {
const db = drizzle(c.env.DB);
await seed(db);
return c.json({ ok: true });
});-- seed.sql
-- Run: npx wrangler d1 execute DB_NAME --local --file=./scripts/seed.sql
-- Clear existing (reverse order)
DELETE FROM comments;
DELETE FROM posts;
DELETE FROM users;
-- Users
INSERT INTO users (id, name, email, created_at) VALUES
('uuid-1', 'Sarah Chen', 'sarah@example.com', '2025-01-15T10:30:00Z'),
('uuid-2', 'James Wilson', 'james@example.com', '2025-02-01T14:22:00Z');
-- Posts (max 10 rows per INSERT for D1)
INSERT INTO posts (id, user_id, title, body, created_at) VALUES
('post-1', 'uuid-1', 'Getting Started', 'Welcome to...', '2025-03-01T09:00:00Z');// Option A: Delete-then-insert (simple, loses data)
await db.delete(schema.users);
await db.insert(schema.users).values(seedUsers);
// Option B: Upsert (preserves non-seed data)
for (const user of seedUsers) {
await db.insert(schema.users)
.values(user)
.onConflictDoUpdate({ target: schema.users.id, set: user });
}| Gotcha | Solution |
|---|---|
| Max ~10 rows per INSERT | Batch inserts in chunks of 10 |
| No native BOOLEAN | Use INTEGER (0/1) |
| No native DATETIME | Use TEXT with ISO 8601 strings |
| JSON stored as TEXT | |
| Foreign keys always enforced | Insert parent tables first |
| 100 bound parameter limit | Keep batch size × columns < 100 |