SQL for Recent Seated Diners | Dataford Interview Questions

OpenTable wants a category-level report of diners who were seated recently. Write a SQL query to calculate the total number of seated diners for each restaurant category during the inclusive 30-day period ending on September 15, 2026.

Output

Return one row per restaurant category, including categories with no qualifying seated diners.
Include restaurant_category and total_seated_diners columns.
Include only reservations with status seated and reservation dates from August 16, 2026 through September 15, 2026, inclusive.
Sum non-NULL party_size values. Treat categories with no qualifying diners as having a total of zero.
Sort the result alphabetically by restaurant_category.

Schema

restaurant_categories

Column	Type	Description
category_idPK	INT	Unique restaurant category identifier
category_name	VARCHAR(100)	Restaurant category name

restaurants

Column	Type	Description
restaurant_idPK	INT	Unique restaurant identifier
restaurant_name	VARCHAR(150)	OpenTable restaurant name
category_id	INT	Restaurant category identifier

reservations

Column	Type	Description
reservation_idPK	INT	Unique reservation identifier
restaurant_id	INT	Reserved restaurant identifier
reservation_date	DATE	Date of the reservation
status	VARCHAR(30)	Reservation outcome or current status
party_size	INT	Number of diners in the reservation

Your question is SQL for Recent Seated Diners. Start with the requirements and the three tables in the Question tab.

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