SQL Month-over-Month Growth | Dataford Interview Questions

Your question is SQL Month-over-Month Growth. Start with the requirements and the two tables on the right.

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Problem

GoFundMe’s Marketing Analytics team wants to monitor the monthly creation of new donation campaigns. Write a PostgreSQL query that calculates month-over-month growth across the full campaign date range.

Requirements

Count eligible campaigns by calendar month using created_at.
Exclude campaigns with status = 'deleted' and campaigns attributed to the test source type. Treat campaigns without a source record as organic.
Include months with zero eligible campaigns between the first and last eligible campaign month.
Return the current count, prior-month count, and growth percentage. Return NULL for growth when there is no prior month or the prior count is zero.

Schema

campaigns

Column	Type	Description
campaign_idPK	INTEGER	Unique GoFundMe campaign identifier
title	VARCHAR(150)	Campaign title
created_at	TIMESTAMP	Timestamp when the campaign was created
status	VARCHAR(20)	Campaign lifecycle status

campaign_sources

Column	Type	Description
source_idPK	INTEGER	Unique source attribution record
campaign_id	INTEGER	Referenced GoFundMe campaign
source_type	VARCHAR(30)	Campaign acquisition source