Month-over-Month Revenue Growth in SQL | Dataford Interview Questions

Boston Consulting Group's Financial Planning and Analysis team wants to monitor revenue trends for the Strategy practice area. Write a PostgreSQL query that calculates monthly revenue and month-over-month growth.

Requirements

Filter results to the Strategy practice area and calendar year 2024.
Aggregate revenue by calendar month.
Show the previous month's revenue and growth percentage. Return NULL for the first month or when the previous month's revenue is zero.
Order results chronologically.

Schema

practice_areas

Column	Type	Description
practice_area_idPK	INT	Unique practice area identifier
practice_name	VARCHAR(100)	BCG consulting practice name

engagement_revenue

Column	Type	Description
revenue_idPK	INT	Unique revenue record identifier
practice_area_id	INT	Referenced practice area
engagement_code	VARCHAR(20)	BCG engagement reference code
revenue_date	DATE	Date revenue was recognized
revenue_amount	NUMERIC(12,2)	Recognized revenue amount

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