Du behöver inte initiera variabeln i underfrågan. Du kan istället initiera variabeln med CROSS JOIN
:
SELECT time_of_day,
@channel_rank := IF(@current_channel = channel, 1,
@channel_rank + 1) AS channel_rank,
@current_channel := channel AS channel,Views
FROM
(
SELECT time_of_day,channel, SUM(Views) AS 'Views'
FROM access_logs_meaningful_optimized
WHERE `time_of_day` = 0
AND playing_date = '2016-10-26'
GROUP BY channel
ORDER BY SUM(views) DESC
LIMIT 5
) AS xx
CROSS JOIN (SELECT @channel_rank := 0) var