Reverse Rows in a DataFrame | Dataford Interview Questions

Your question is Reverse Rows in a DataFrame. Start with the requirements and the two tables on the right.

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Problem

Protium's analytics team receives repayment events in chronological order but sometimes needs to display each loan's event rows in reverse order for investigation. Write a PostgreSQL query that reverses the event sequence independently for every active loan.

Requirements

Use a window function to establish each loan's chronological event order, using event_date and event_id as a deterministic tie-breaker.
Return active loans, including active loans with no repayment events.
Assign reversed_position = 1 to the latest event for each loan, and preserve the original event details.
Order the final result by loan_id and reversed position, placing loans without events last within their loan ordering.

Schema

loans

Column	Type	Description
loan_idPK	INTEGER	Unique Protium loan identifier
borrower_name	VARCHAR(100)	Borrower's name
status	VARCHAR(20)	Current loan status

repayment_events

Column	Type	Description
event_idPK	INTEGER	Unique repayment event identifier
loan_id	INTEGER	Referenced loan identifier
event_date	DATE	Date the event was recorded
event_type	VARCHAR(30)	Repayment event category
amount	NUMERIC(10,2)	Event amount, which may be NULL