SELECT *,substring(time,0,16) as time,
CASE
WHEN TEM < 25 THEN 1
WHEN TEM > 27 THEN 1
WHEN HUM < 45 THEN 1
END AS leval,
FROM demo
WHERE leval != NULL
GROUP BY SN, TUMBLINGWINDOW(MI, 30);
请教一下，我这样写SQL语句系统会记录30分钟内的第一条数据，如果我希望记录30分钟内的最后一条符合条件的数据，应该怎么完善SQL语句呢