Consecutive Months MAU SQL | Dataford Interview Questions

Write a SQL query to find the monthly active users on the Starbucks Rewards app who made purchases in consecutive months.

Use the users and purchases tables. Treat consecutive months as adjacent calendar months, regardless of the specific purchase dates. Multiple purchases by the same user in one month count once.

Output

One row per month with qualifying users
Columns: month_start and monthly_active_users
Include only months with at least one qualifying user
Order by month_start ascending

Schema

users

Column	Type	Description
user_idPK	INT	Unique Starbucks Rewards app user identifier
user_name	VARCHAR(100)	User display name

purchases

Column	Type	Description
purchase_idPK	INT	Unique purchase identifier
user_id	INT	User who made the purchase
purchase_date	DATE	Date of purchase
purchase_channel	VARCHAR(30)	Purchase channel

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