SQL for New Devices | Dataford Interview Questions

Given three tables, write a SQL query to find new devices that occurred in a specific month.

Determine each device's first recorded event and return devices whose first event occurred during March 2025.

Output

One row per qualifying device with device_id, device_name, device_type, and first_seen_at.
Include devices with no recorded type, labeling the type Unknown.
Order by first_seen_at ascending, then device_id ascending.

device_events

Column	Type	Description
event_idPK	INT	Unique event identifier
device_id	INT	Device that generated the event
occurred_at	TIMESTAMP	Timestamp when the event occurred
event_type	VARCHAR(40)	Category of device event

devices

device_types

Column	Type	Description
type_idPK	INT	Unique device type identifier
type_name	VARCHAR(60)	Name of the device type

Your question is SQL for New Devices. Start with the requirements and the three 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.