De-duplicate Multi-Device Playback Logs

SQL practice question · Hard · Data Cleaning · Netflix

The same play (same profile_id, title_id and started_at) can be reported by several clients. `source` is messy text: compare it as lower(trim(source)). Keep ONE row per play using priority 'tv' first, then 'web', then 'mobile'; within the same source keep the larger `watched_min` (NULL counts as 0), then the lower `log_id`. From the kept rows return per profile: `profile_id`, `plays`, `total_watch_min` (NULL as 0), `tv_share_pct` = ROUND(100.0 * plays whose kept source is 'tv' / plays, 1). Order by `profile_id`.

Table: playback_logs

Schema of playback_logs
ColumnType
log_idINTEGER
profile_idINTEGER
title_idINTEGER
started_atTIMESTAMP
sourceTEXT
watched_minINTEGER
Sample rows of playback_logs
log_idprofile_idtitle_idstarted_atsourcewatched_min
119002026-11-01 20:00:00mobile50
219002026-11-01 20:00:00tv45
319012026-11-01 21:00:00web30
419012026-11-01 21:00:00mobile31
529002026-11-02 08:00:00mobile20
629022026-11-02 09:00:00tv60
729022026-11-02 09:00:00tv58
Expected output on the sample data
profile_idplaystotal_watch_mintv_share_pct
127550
228050

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