Nested SQL for Data Work | Dataford Interview Questions

Tell me about your experience writing nested queries and subqueries in SQL.

For a hands-on response, write a PostgreSQL query that returns providers whose completed appointment count is greater than the average completed appointment count across all providers, including providers with zero completed appointments. Appointments with a NULL status do not count as completed.

Output

One row per qualifying provider.
Columns: provider_id, provider_name, and completed_appointment_count.
Include only providers above the overall average, ordered by count descending, then provider_id ascending.

Schema

providers

Column	Type	Description
provider_idPK	INT	Unique provider identifier
provider_name	VARCHAR(100)	Provider display name

appointments

Column	Type	Description
appointment_idPK	INT	Unique appointment identifier
provider_id	INT	Provider assigned to the appointment
status	VARCHAR(30)	Appointment status

Your question is Nested SQL for Data Work. Start with the requirements and the two tables in the Question tab.

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

Problem