Top Power Users Query | Dataford Interview Questions

The TELUS Digital AI Community wants to identify its most active contributors for the completed second quarter of 2025. Write a PostgreSQL query that ranks users by the number of activity events recorded during Q2 2025 and returns the top 10%.

Requirements

Include all users in the population, including users with no qualifying activity.
Count only events from 2025-04-01 through 2025-06-30, inclusive.
Rank users by activity count in descending order, using user_id as a deterministic tie-breaker.
Return the smallest whole-number group representing at least 10% of all users, with the user ID, display name, activity count, and rank.

Schema

users

Column	Type	Description
user_idPK	INTEGER	Unique user identifier
display_name	VARCHAR(100)	User's display name
email	VARCHAR(255)	User email address
joined_at	DATE	Date the user joined

activity_events

Column	Type	Description
event_idPK	INTEGER	Unique activity event identifier
user_id	INTEGER	User associated with the event
event_type	VARCHAR(50)	Type of activity performed
occurred_at	TIMESTAMP	Timestamp when the activity occurred

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