select * from data where sn='221' order by id desc limit 4
idsntspqvaluesystemts
29380308 221 temp 12.80 1576446327 Sun 15 12 2019 22:45:27
29380307 221 hum 34.20 1576446327 Sun 15 12 2019 22:45:27
29380296 221 hum 34.30 1576446307 Sun 15 12 2019 22:45:07
29380295 221 temp 12.80 1576446307 Sun 15 12 2019 22:45:07

Sun Dec 15 22:46:29 2019 by walley