Cohort First and Last Interactions | Dataford Interview Questions

Using SQL window functions, identify the first and last interaction dates for users within a specific cohort.

Use cohort 2025-Q1. Include every user in that cohort, including users with no dated interactions. Ignore interactions whose date is NULL.

Output

One row per user in the cohort, with user_id, first_interaction_date, and last_interaction_date.
Return NULL dates when a user has no qualifying interactions.
Order by user_id ascending.

users

Column	Type	Description
user_idPK	INT	Unique user identifier
cohort_name	VARCHAR(20)	Cohort assigned to the user

interactions

Column	Type	Description
interaction_idPK	INT	Unique interaction identifier
user_id	INT	User associated with the interaction
interaction_date	DATE	Calendar date of the interaction
interaction_type	VARCHAR(30)	Type of interaction recorded

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