SQL for Weekly Throughput | Dataford Interview Questions

Write a SQL query to track weekly project throughput by team at Condé Nast, including completed tasks, average cycle time, and week-over-week change.

Use the provided teams and tasks data. Include completed tasks only, calculate cycle time from task start to completion, and compare each team's weekly completed-task count with its previous reported week.

Output

One row per team and reported week.
Columns: team_name, week_start, completed_tasks, avg_cycle_time_hours, and wow_change_pct.
Sort by team_name, then week_start ascending. Return NULL when a prior week is unavailable or cycle time cannot be calculated.

Schema

teams

Column	Type	Description
team_idPK	INT	Unique team identifier
team_name	VARCHAR(100)	Condé Nast team name

tasks

Column	Type	Description
task_idPK	INT	Unique task identifier
team_id	INT	Team assigned to the task
status	VARCHAR(30)	Current task status
started_at	TIMESTAMP	Timestamp when work began
completed_at	TIMESTAMP	Timestamp when the task was completed

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Problem