SQL Conversion Rate by Segment | Dataford Interview Questions

Write a SQL query to calculate the conversion rate by customer segment over a specific time period for Rivian marketing campaigns.

Assume a customer is exposed when a campaign event exists during the period, and converted when that event has converted = TRUE. Use the period from 2025-01-01 through 2025-03-31, inclusive.

Output

One row per customer segment, including segments with no qualifying events.
Columns: segment, exposed_customers, converted_customers, and conversion_rate_pct.
Return conversion rate as a percentage rounded to two decimals, order by segment ascending, and place a NULL segment last.

Schema

customers

Column	Type	Description
customer_idPK	INT	Unique customer identifier
customer_name	VARCHAR(100)	Customer name
segment	VARCHAR(50)	Customer marketing segment

campaign_events

Column	Type	Description
event_idPK	INT	Unique campaign event identifier
customer_id	INT	Customer associated with the campaign event
campaign_name	VARCHAR(100)	Rivian marketing campaign name
event_date	DATE	Date of campaign exposure or conversion event
converted	BOOLEAN	Whether the campaign event resulted in a conversion

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Problem