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This question evaluates proficiency in SQL data manipulation, including time-windowed aggregation, joins, filtering by status and date, and percentile-based ranking of restaurant revenue using completed orders.

  • medium
  • DoorDash
  • Data Manipulation (SQL/Python)
  • Data Scientist

Find orders from bottom-quartile revenue restaurants

Company: DoorDash

Role: Data Scientist

Category: Data Manipulation (SQL/Python)

Difficulty: medium

Interview Round: Onsite

## SQL Question You want to identify **orders coming from restaurants whose total revenue is in the bottom 25th percentile**. Assume the following tables: ### `restaurants` - `restaurant_id` (BIGINT, PK) - `name` (VARCHAR) - `market_id` (BIGINT) ### `orders` - `order_id` (BIGINT, PK) - `restaurant_id` (BIGINT, FK → restaurants.restaurant_id) - `customer_id` (BIGINT) - `order_total` (DECIMAL(10,2)) — revenue for this order (exclude tips) - `created_at` (TIMESTAMP) - `status` (VARCHAR) — e.g., 'completed', 'canceled' ## Task Write a SQL query to return orders from restaurants whose **total completed-order revenue** is in the **bottom 25%** among all restaurants over a specified analysis window. ### Requirements - Use an analysis window of the **last 30 days** relative to `CURRENT_DATE`. - Consider only `status = 'completed'` orders. - Define restaurant revenue as `SUM(order_total)` over the window. - Compute the **25th percentile** of restaurant revenue across restaurants with ≥1 completed order in the window. ### Output columns - `order_id` - `restaurant_id` - `order_total` - `created_at` - `restaurant_revenue_30d` State any assumptions (e.g., percentile function availability in your SQL dialect).

Quick Answer: This question evaluates proficiency in SQL data manipulation, including time-windowed aggregation, joins, filtering by status and date, and percentile-based ranking of restaurant revenue using completed orders.

Last updated: Jun 4, 2026

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