Session Duration in SQL | Dataford Interview Questions

Given a series of user events, how would you calculate session duration using SQL?

Assume a new session begins when a user has more than 30 minutes of inactivity. Exclude events with a missing user ID or event timestamp, and return one row per session.

Output

Columns: user_id, session_number, session_start, session_end, and duration_seconds
Include each valid user session, ordered by user_id, then session_start, then session_number

Schema

user_events

Column	Type	Description
event_idPK	INT	Unique identifier for the event
user_id	VARCHAR(30)	Identifier of the user who generated the event
event_time	TIMESTAMPTZ	Timestamp when the event occurred
event_name	VARCHAR(40)	Name of the recorded user event

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