A reservation system that actually handles availability: room types versus rooms, rate plans, a per-night rate and inventory calendar, reservations broken down by night, payments and verified reviews.
A production-shaped e-commerce schema: products with variants, inventory per location, carts, orders with snapshotted line items, payments and shipments. Open it in the editor or export SQL for six dialects.
The core of an electronic health record: patients and providers, appointments versus encounters, coded conditions and observations, prescriptions against a drug catalogue, allergies and insurance coverage over time.
A Jira-shaped tracker: projects with human-readable issue keys, subtasks through a self-reference, fractional board positions for drag-and-drop, labels, milestones, comments, attachments and a worklog.
A vehicle rental schema: branches, vehicle classes versus the individual cars behind them, a per-branch availability calendar, reservations and signed agreements, mileage and fuel, damage inspections with photos, protection add-ons and one-way fees.