Mid-Level SQL Skills | Dataford Interview Questions

What are some common mid-level SQL questions you can answer?

For this exercise, write one PostgreSQL query that summarizes qualifying customer orders during the first quarter of 2025. Include only customers with at least two completed orders in that period.

Output

One row per qualifying customer, with customer_id, customer_name, completed_order_count, total_amount, average_order_amount, and spending_tier.
spending_tier must be High for totals of at least 500, Medium for totals from 250 through 499.99, and Low otherwise.
Sort by total_amount descending, then customer_id ascending.

Schema

customers

Column	Type	Description
customer_idPK	INT	Unique customer identifier
customer_name	VARCHAR(100)	Customer display name
region	VARCHAR(30)	Customer region

orders

Column	Type	Description
order_idPK	INT	Unique order identifier
customer_id	INT	Customer who placed the order
order_date	DATE	Date the order was placed
order_status	VARCHAR(20)	Order state
amount	NUMERIC(10,2)	Order amount

Your question is Mid-Level SQL Skills. Start with the requirements and the two tables in the Question tab.

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Problem