Advanced SQL Topics | Dataford Interview Questions

Explain advanced SQL concepts you would use for data engineering tasks.

Using the provided customers and orders tables, write a query that summarizes completed 2025 sales for every customer, including customers with no qualifying orders. The result should demonstrate sales aggregation, regional ranking, null handling, and customer segmentation.

Output

One row per customer with customer_id, customer_name, region, completed_orders, total_completed_sales, region_rank, and sales_segment.
Include all customers, rank ties equally within each region, and classify sales as Platinum, Gold, Silver, or Bronze.
Order by region, region_rank, and customer_id.

Schema

customers

Column	Type	Description
customer_idPK	INT	Unique customer identifier
customer_name	VARCHAR(100)	Customer name
region	VARCHAR(50)	Customer sales region

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
order_total	NUMERIC(10,2)	Order monetary total
status	VARCHAR(20)	Order processing status

Your question is Advanced SQL Topics. Start with the requirements and the two tables in the Question tab.

Run and submit as often as you like. When you're ready, talk me through your approach or go straight to the code.

Problem