Top 5 Customers in 90 Days | Dataford Interview Questions

Your question is Top 5 Customers in 90 Days. Start with the requirements and the two tables on the right.

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Problem

Intelliswift wants a recent-spend leaderboard for customers using its customer analytics data. Write a PostgreSQL query to identify the five customers with the highest completed-order spend during the last 90 days.

Requirements

Include only orders from the last 90 days, including today, based on CURRENT_DATE.
Include only orders with status = 'completed'.
Aggregate order amounts by customer, sort from highest to lowest spend, and return exactly five customers when at least five qualify.
Use a deterministic secondary sort by customer_id for tied totals.

Schema

customers

Column	Type	Description
customer_idPK	INT	Unique customer identifier
customer_name	VARCHAR(100)	Customer's full name
email	VARCHAR(150)	Customer email address

orders

Column	Type	Description
order_idPK	INT	Unique order identifier
customer_id	INT	Customer associated with the order
order_date	DATE	Date the order was placed
total_amount	NUMERIC(12,2)	Total monetary value of the order
status	VARCHAR(20)	Order processing status