Each genre's share of listening time

Constraints

1. 1minutes is the genre's ms_played divided by 60000, rounded to 1 decimal place.
2. 2pct_of_total is the genre's share of all listening time, rounded to 1 decimal place. The four values add up to 100.
3. 3Listening time means ms_played — not the number of plays, and not duration_ms.
4. 4Divide the raw sums and round the result. Rounding first and dividing the rounded figures gives shares that do not sum to 100.
5. 5Every genre with at least one play appears.
6. 6Order by pct_of_total descending, then genre.

Worked example

jazz accumulates 2,130,000 ms — 35.5 minutes of the platform's 118.2-minute total — so pct_of_total is 30.0. The instinct is to compute the total in a subquery that re-reads stream_plays. That works and scans the table a second time for a number the query already holds; SUM(...) OVER () takes it from the rows in front of it.

What this tests

An unpartitioned window — SUM(...) OVER () — used to place a grand total beside every grouped row, which is how a share is computed without a self-join or a second pass over the source table.