Peringkat pemain berdasarkan kategori selama berbulan-bulan

Anda memerlukan variabel pengguna lain untuk memberi tahu Anda saat itu di bulan baru.

SET @rownumber := 0;
SET @month := 0;

SELECT pla.event_date, 
  @rownumber := IF(@month=MONTH(pla.event_date), @rownumber + 1, 1) AS rank, 
  @month := MONTH(pla.event_date) AS month,
  pla.kills, pla.player_id
FROM player AS pla
INNER JOIN ...
WHERE pla.event_date >= '2017-09-01' AND pla.event_date <= '2017-12-31'
ORDER BY MONTH(pla.event_date), pla.kills DESC