select * from data where sn='221' order by id desc limit 4
idsntspqvaluesystemts
20705223 221 temp 16.40 1558467775 Tue 21 05 2019 21:42:55
20705222 221 hum 55.60 1558467775 Tue 21 05 2019 21:42:55
20705218 221 temp 16.40 1558467774 Tue 21 05 2019 21:42:54
20705217 221 hum 55.40 1558467774 Tue 21 05 2019 21:42:54

Tue May 21 21:43:01 2019 by walley