ETL And Data Cleaning | Dataford Interview Questions

Tell me about your experience with ETL, data cleaning, and SQL.

Use the tables below to identify valid orders and summarize customer-level data. Treat rows with missing customer_id, negative amount, or invalid status as invalid. Keep only valid orders in the result.

Output

One row per customer.
Columns: customer_id, customer_name, valid_order_count, total_valid_amount, latest_valid_order_date.
Include only customers with at least one valid order.
Sort by total_valid_amount descending, then customer_id ascending.

Schema

customers

Column	Type	Description
customer_idPK	INT	Unique customer identifier
customer_name	VARCHAR(255)	Customer display name
region	VARCHAR(100)	Customer region

orders

Column	Type	Description
order_idPK	INT	Unique order identifier
customer_id	INT	Customer identifier from the source system
order_date	DATE	Date the order was created
amount	DECIMAL(10,2)	Order amount
status	VARCHAR(20)	Order processing status

Your question is ETL And Data Cleaning. Start with the requirements and the two tables in the Question tab.

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Problem