CREATE TABLE Products_for_hire (product_id VARCHAR2, booked_amount NUMBER)
CREATE TABLE products_booked (product_id VARCHAR2, booked_amount NUMBER)

How many products are never booked with amount higher than 200?
SELECT COUNT(*) FROM Products_for_hire WHERE NOT product_id IN (SELECT product_id FROM products_booked WHERE booked_amount > 200)
SELECT COUNT(*) FROM "Products_for_hire" WHERE NOT "product_id" IN (SELECT "product_id" FROM "products_booked" WHERE "booked_amount" > 200)