After the third bug accounting asked: «let the database itself reject products priced at or below zero» — it's more reliable than validating in application code. Build products with id (primary key), name (up to 100 chars), and price (number with two decimals), then add a constraint products_price_positive that forbids rows with price ≤ 0. After that any attempt to insert a row with zero or negative price fails with an error.