Start by clarifying the schema and assumptions, then break the problem into two parts: computing distinct cars rented per city and car size on the given date, and computing total active inventory per city and car size. Use conditional aggregation and handle NULL dropoff by treating it as still rented, and use NULLIF or CASE to avoid division by zero when calculating utilization rate.
Pro tip: Mention that you would validate the query with edge cases like no rentals or no inventory, and consider indexing on rental date and car size for performance. Also, clarify whether 'active inventory' means cars available for rent or total cars in the fleet, as this affects the denominator.
Ask about table structures, column names, and what 'active inventory' means. Confirm that a rental is active on the date if pickup_date <= date AND (dropoff_date IS NULL OR dropoff_date > date).
Write a subquery that selects city, car_size, and counts distinct car_id from rentals joined with cars and locations, filtering for the specific date and active rentals.
Write another subquery that counts total cars per city and car size from the cars and locations tables, assuming all cars are part of the inventory.
Join the two subqueries on city and car_size, and compute utilization as rented_count / NULLIF(total_inventory, 0) to avoid division by zero.
Use COALESCE to handle NULLs from left joins, and ensure the query returns 0 for utilization when inventory is zero. Consider performance implications and indexing.
AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.