select * from data where sn='221' and pq='ts' order by id desc limit 4
idsntspqvaluesystemts
20700227 221 ts 1558459220 1558459220 Tue 21 05 2019 19:20:20
20694284 221 ts 1558449040 1558449040 Tue 21 05 2019 16:30:40
20694275 221 ts 1558449020 1558449020 Tue 21 05 2019 16:30:20
20694270 221 ts 1558449019 1558449019 Tue 21 05 2019 16:30:19

Tue May 21 21:04:21 2019 by walley