Optimizing Complex SQL Queries | Dataford Interview Questions

Can you explain your experience with SQL and how you optimize complex queries?

Use the provided customers and orders tables as a hands-on example. Return active customers whose completed orders since 2025-01-01 meet both the minimum order-count and spending requirements.

Output

One row per qualifying active customer.
Columns: customer_name, order_count, total_completed, last_order_date, and spending_tier.
Include customers with at least 2 qualifying orders and at least 500 total completed value.
Classify totals of at least 1,000 as high, otherwise standard.
Sort by total_completed descending, then customer_name ascending.

Schema

customers

Column	Type	Description
customer_idPK	INT	Unique customer identifier
customer_name	VARCHAR(100)	Customer display name
account_status	VARCHAR(20)	Current account status
customer_segment	VARCHAR(30)	Customer segment

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
status	VARCHAR(20)	Order processing status
amount	NUMERIC(12,2)	Order value

Your question is Optimizing Complex SQL Queries. 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