SQL and Python Data Manipulation | Dataford Interview Questions

How would you manipulate data using SQL and Python?

Using the provided merchants, payments, and refunds tables, produce the requested January 2025 merchant-level results in PostgreSQL. Include merchants with no qualifying payment attempts. The SQL result should be reproducible in Python using equivalent tabular data manipulation.

Output

One row per merchant, including merchants without January payment attempts
Columns: merchant_id, merchant_name, payment_attempts, successful_payments, captured_amount, refund_amount, net_amount, and success_rate_pct
Include January payment activity and January refunds, order by captured_amount descending, then merchant_id ascending

Schema

merchants

Column	Type	Description
merchant_idPK	INT	Unique merchant identifier
merchant_name	VARCHAR(100)	Merchant display name

payments

Column	Type	Description
payment_idPK	INT	Unique payment identifier
merchant_id	INT	Merchant receiving the payment
payment_date	DATE	Date the payment was created
status	VARCHAR(20)	Payment processing status
amount	NUMERIC(12,2)	Payment amount

refunds

Column	Type	Description
refund_idPK	INT	Unique refund identifier
payment_id	INT	Payment associated with the refund
refund_date	DATE	Date the refund was issued
amount	NUMERIC(12,2)	Refund amount

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Problem