select * from data where sn='221' and pq='ts' order by id desc limit 4
idsntspqvaluesystemts
18872941 221 ts 1553483694 1553483694 Mon 25 03 2019 04:14:54
18869617 221 ts 1553477910 1553477910 Mon 25 03 2019 02:38:30
18816780 221 ts 1553387560 1553387560 Sun 24 03 2019 01:32:40
18771065 221 ts 1553309679 1553309679 Sat 23 03 2019 03:54:39

Mon Mar 25 06:38:36 2019 by walley