select * from data where sn='221' order by id desc limit 4
idsntspqvaluesystemts
18878970 221 temp 12.40 1553494053 Mon 25 03 2019 07:07:33
18878969 221 hum 52.80 1553494053 Mon 25 03 2019 07:07:33
18878959 221 hum 52.80 1553494033 Mon 25 03 2019 07:07:13
18878958 221 temp 12.40 1553494033 Mon 25 03 2019 07:07:13

Mon Mar 25 07:07:40 2019 by walley