select * from data where sn='221' order by id desc limit 4
idsntspqvaluesystemts
29379461 221 temp 12.90 1576445067 Sun 15 12 2019 22:24:27
29379460 221 hum 34.00 1576445067 Sun 15 12 2019 22:24:27
29379449 221 hum 33.80 1576445047 Sun 15 12 2019 22:24:07
29379448 221 temp 12.90 1576445047 Sun 15 12 2019 22:24:07

Sun Dec 15 22:24:44 2019 by walley