How to Seed PostgreSQL with Realistic Test Data

The Problem

PostgreSQL is the world's most advanced open source database, but seeding it with realistic test data is still a manual chore. You end up writing long INSERT statements, or building a script that generates random strings that look nothing like real names, emails, or addresses.

Handling foreign keys makes it worse. You need to insert the parent table first, collect the generated IDs, and then use those when inserting the child table. A single mistyped UUID and your seed script throws a constraint violation.

The Solution: MockHero API

MockHero generates realistic data for any PostgreSQL schema. Define tables, use 156+ field types, connect them with ref fields, and request SQL output to pipe directly into psql. No libraries, no scripts.

Quick Setup

curl -X POST https://api.mockhero.dev/api/v1/generate \
  -H "x-api-key: mh_your_api_key" \
  -H "Content-Type: application/json" \
  -d '{
  "tables": [
    {
      "name": "departments",
      "count": 5,
      "fields": [
        { "name": "id", "type": "uuid" },
        { "name": "name", "type": "department" },
        { "name": "budget", "type": "decimal", "params": { "min": 50000, "max": 500000 } }
      ]
    },
    {
      "name": "employees",
      "count": 25,
      "fields": [
        { "name": "id", "type": "uuid" },
        { "name": "department_id", "type": "ref", "params": { "ref": "departments.id" } },
        { "name": "name", "type": "full_name" },
        { "name": "email", "type": "email" },
        { "name": "salary", "type": "integer", "params": { "min": 40000, "max": 150000 } },
        { "name": "hired_at", "type": "date_past" }
      ]
    }
  ],
  "format": "sql"
}'

Step-by-Step Guide

1. Prerequisites

You need psql and curl installed. Both ship with most Linux and macOS distributions.

2. Get your MockHero API key

Sign up at mockhero.dev/sign-up and copy your key.

3. Create your tables

CREATE TABLE departments (
  id UUID PRIMARY KEY,
  name TEXT NOT NULL,
  budget NUMERIC NOT NULL
);

CREATE TABLE employees (
  id UUID PRIMARY KEY,
  department_id UUID REFERENCES departments(id),
  name TEXT NOT NULL,
  email TEXT NOT NULL,
  salary INTEGER NOT NULL,
  hired_at DATE NOT NULL
);

4. Generate and insert data

Use the curl command from Quick Setup. The format: "sql" option returns INSERT statements you pipe directly into psql.

5. Verify

psql $DATABASE_URL -c "SELECT e.name, d.name AS dept FROM employees e JOIN departments d ON d.id = e.department_id LIMIT 5;"

Complete Example

For a script-based approach, save the curl command to seed.sh and run it whenever you need fresh data. The SQL output mode means zero JavaScript dependencies.

Why MockHero vs Faker / Manual Seeds

• Zero dependencies — SQL output pipes directly into psql, no Node.js required.
• Referential integrity — ref fields ensure every foreign key is valid.
• Production-quality values — real-looking names, emails, and dates instead of "test123".

Get Started

Free tier, 1,000 rows/month. Sign up at mockhero.dev and pipe realistic data into your PostgreSQL database today.