Average Workout Duration per Treadmill

Problem

Table: `treadmill_log`

| Column Name | Type |
|---|---|
| treadmill_id | int |
| session_id | int |
| phase | text |
| moment | float |

`(treadmill_id, session_id, phase)` is the primary key. Each treadmill in a gym records two rows per workout session: one row with `phase = 'start'` and one with `phase = 'finish'`, where `moment` is the timestamp in seconds.

For every treadmill, compute the **average workout duration** across all of its sessions. The duration of a session is its finish timestamp minus its start timestamp. Round the answer to 3 decimal places and alias it `avg_duration`. Return one row per treadmill.

Tables

Example rows — the live problem includes the full dataset.

Expected output

Your answer should return 2 rows with the columns treadmill_id, avg_duration.

Starter code (SQL)

SELECT *
FROM treadmill_log;

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