Top N Users Per Day | Dataford Interview Questions

Your question is Top N Users Per Day. Start with the requirements and the two tables on the right.

Run and submit as often as you like. When you're ready, talk me through your approach or go straight to the code.

Problem

Databricks administrators want a daily view of the users generating the most activity in Databricks SQL. Write a PostgreSQL query that counts valid activity events per user and returns the top three activity ranks for each calendar day.

Requirements

Join activity_logs to users so the output includes each user's name.
Count only events with a non-null activity_type, grouped by user and activity date.
Use a ranking window function so ties at the third rank are included.
Return activity_date, user_id, user_name, and activity_count, ordered by date, rank, and user ID.

Schema

users

Column	Type	Description
user_idPK	INTEGER	Unique Databricks user identifier
user_name	VARCHAR(100)	User display name
email	VARCHAR(255)	User email address

activity_logs

Column	Type	Description
activity_idPK	INTEGER	Unique activity event identifier
user_id	INTEGER	User associated with the activity event
activity_at	TIMESTAMP	Timestamp when the activity occurred
activity_type	VARCHAR(50)	Type of activity, nullable when event metadata is incomplete