Watch Sessions with 30-Minute Timeout

SQL practice question · Hard · Date & Time · Netflix

Build viewing sessions from raw play events. Events of the same user belong to the same session while the gap to the previous event is 30 minutes or less; a gap of more than 30 minutes starts a new session. Identical (user_id, event_ts) rows are duplicates and count once. Session length = minutes between its first and last event (a single-event session lasts 0). Return `user_id`, `sessions`, `avg_session_min` (ROUND 1). Order by `user_id`.

Table: watch_events

Schema of watch_events
ColumnType
user_idINTEGER
event_tsTIMESTAMP
title_idINTEGER
Sample rows of watch_events
user_idevent_tstitle_id
12026-05-10 20:00:00501
12026-05-10 20:20:00501
12026-05-10 20:50:00502
12026-05-10 22:00:00503
12026-05-10 22:10:00503
22026-05-10 09:00:00501
32026-05-10 23:50:00510
32026-05-11 00:15:00510
Expected output on the sample data
user_idsessionsavg_session_min
1230
210
3125

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