Pre vs Post Launch SQL | Dataford Interview Questions

Write a SQL query to compare pre- and post-launch performance using window functions and date-based grouping.

Use the provided campaign launch dates and daily performance records. Return monthly metrics for each campaign, identify whether each month is before or after launch, and compare each month with the previous month.

Output

One row per campaign and performance month, with campaign_id, campaign_name, performance_month, launch_phase, total_impressions, total_conversions, conversion_rate_pct, prior_month_conversion_rate_pct, and rate_change_pct.
Include only campaigns with performance records, ordered by campaign_id and performance_month ascending.

Schema

campaigns

Column	Type	Description
campaign_idPK	INT	Unique campaign identifier
campaign_name	VARCHAR(100)	Campaign name
launch_date	DATE	Date the campaign launched

campaign_daily_performance

Column	Type	Description
performance_idPK	INT	Unique daily performance record identifier
campaign_id	INT	Referenced campaign identifier
performance_date	DATE	Date of the performance record
impressions	INT	Number of ad impressions
conversions	INT	Number of attributed conversions

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Problem