SQL for Weekly Team Performance | Dataford Interview Questions

Duolingo's Operations Manager needs a weekly view of operational task performance across teams supporting the Duolingo app, Duolingo Max, and the Duolingo English Test. Write a PostgreSQL query that joins task records with team metadata and calculates completion rates for January 2025.

Requirements

Group results by Monday-based week and team.
Return total tasks, completed tasks, and completion rate as a percentage rounded to one decimal place.
Include only tasks assigned during January 2025 and only tasks associated with a known team.
Sort results by week and team name.

Schema

teams

Column	Type	Description
team_idPK	INTEGER	Unique team identifier
team_name	VARCHAR(100)	Operations team name
region	VARCHAR(50)	Primary operating region
operating_model	VARCHAR(50)	How the team operates

tasks

Column	Type	Description
task_idPK	INTEGER	Unique task identifier
team_id	INTEGER	References teams.team_id
task_type	VARCHAR(50)	Operational task category
assigned_at	DATE	Date the task was assigned
status	VARCHAR(20)	Current task status

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Problem