db-seed
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'.
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Install
Works with every agent the skills CLI supports.
npx skills add https://github.com/jezweb/claude-skills --skill db-seed- 01
Install
Run the command in your project. The CLI asks which agents to install for.
- 02
Describe the task
Ask your agent for something this skill covers. It loads db-seed automatically when relevant.
- 03
Review the result
The agent follows the SKILL.md steps, scripts and references bundled with the skill.
SKILL.md
The instructions your agent reads when the skill is triggered.
Database Seed Generator
Generate seed scripts that populate databases with realistic, domain-appropriate sample data. Reads your schema and produces ready-to-run seed files.
Workflow
1. Find the Schema
Scan the project for schema definitions:
| Source | Location pattern |
|---|---|
| Drizzle schema | src/db/schema.ts, src/schema/*.ts, db/schema.ts |
| D1 migrations | drizzle/*.sql, migrations/*.sql |
| Raw SQL | schema.sql, db/*.sql |
| Prisma | prisma/schema.prisma |
Read all schema files. Build a mental model of:
- Tables and their columns
- Data types and constraints (NOT NULL, UNIQUE, DEFAULT)
- Foreign key relationships (which tables reference which)
- JSON fields stored as TEXT (common in D1/SQLite)
2. Determine Seed Parameters
Ask the user:
| 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 |
Purpose affects data quality:
- dev: Varied data, some edge cases (empty fields, long strings, unicode)
- demo: Polished data that looks good in screenshots and presentations
- testing: Systematic data covering boundary conditions, duplicates, special characters
3. Plan Insert Order
Build a dependency graph from foreign keys. Insert parent tables before children.
Example order for a blog schema:
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)
Circular dependencies: If table A references B and B references A, use nullable foreign keys and insert in two passes (insert with NULL, then UPDATE).
4. Generate Realistic Data
Do NOT use generic placeholders like "test123", "foo@bar.com", or "Lorem ipsum". Generate data that matches the domain.
Data Generation Patterns (no external libraries needed)
Names: Use a hardcoded list of common names. Mix genders and cultural backgrounds.
const firstNames = ['Sarah', 'James', 'Priya', 'Mohammed', 'Emma', 'Wei', 'Carlos', 'Aisha'];
const lastNames = ['Chen', 'Smith', 'Patel', 'Garcia', 'Kim', 'O\'Brien', 'Nguyen', 'Wilson'];
Emails: Derive from names — sarah.chen@example.com. Use example.com domain (RFC 2606 reserved).
Dates: Generate within a realistic range. Use ISO 8601 format for D1/SQLite.
const randomDate = (daysBack: number) => {
const d = new Date();
d.setDate(d.getDate() - Math.floor(Math.random() * daysBack));
return d.toISOString();
};
IDs: Use crypto.randomUUID() for UUIDs, or sequential integers if the schema uses auto-increment.
Deterministic seeding: For reproducible data, use a seeded PRNG:
function seededRandom(seed: number) {
return () => {
seed = (seed * 16807) % 2147483647;
return (seed - 1) / 2147483646;
};
}
const rand = seededRandom(42); // Same seed = same data every time
Prices/amounts: Use realistic ranges. (rand() * 900 + 100).toFixed(2) for $1-$10 range.
Descriptions/content: Write 3-5 realistic variations per content type and cycle through them. Don't generate AI-sounding prose — write like real user data.
5. Output Format
TypeScript (Drizzle ORM)
// 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`);
}
Run with: npx tsx scripts/seed.ts
For Cloudflare Workers, add a seed endpoint (remove before production):
app.post('/api/seed', async (c) => {
const db = drizzle(c.env.DB);
await seed(db);
return c.json({ ok: true });
});
Raw SQL (D1)
-- 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');
6. Idempotency
Seed scripts must be safe to re-run:
// 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 });
}
Default to Option A for dev/testing, Option B for demo (where users may have added their own data).
D1-Specific Gotchas
| 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 | JSON.stringify() before insert |
| Foreign keys always enforced | Insert parent tables first |
| 100 bound parameter limit | Keep batch size × columns < 100 |
Quality Rules
- Match the domain — an e-commerce seed has products with real-sounding names and prices, not "Product 1"
- Vary the data — don't make every user "John Smith" or every price "$9.99"
- Include edge cases (for testing seeds) — empty strings, very long text, special characters, maximum values
- Reference real IDs — foreign keys must point to actually-inserted parent rows
- Print what was seeded — always log counts so the user knows it worked
- Document the run command — put it in a comment at the top of the file
FAQ
What does the db-seed skill do?
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'.
How do I install db-seed?
Run npx skills add https://github.com/jezweb/claude-skills --skill db-seed in your project. The skills CLI detects the agents you use and copies the skill into the right folder. For Claude Code you can also place the skill folder at ~/.claude/skills/db-seed/ (personal) or .claude/skills/db-seed/ (project).
Which AI agents can use db-seed?
Any agent that supports the open Agent Skills format (a folder with a SKILL.md file), including Claude Code, Codex, Cursor, GitHub Copilot, Gemini CLI, Windsurf, Cline, OpenCode and more.
Is db-seed safe to install?
No partner security audit is available yet. Skills can run commands and scripts, so read the SKILL.md and any bundled files before installing.
Who maintains db-seed?
It is published by jezweb in jezweb/claude-skills. It has 981 recorded installs.
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