process error:
ERROR: OFFSET は負数であってはなりません
SELECT mg.id, mg.title, mg.content, mg.sended_date
FROM unit_mg mg
WHERE mg.areaid='jgiin' AND mg.unitid='soma' AND mg.sended_date is not null AND send_way IN ('now','sched')
ORDER BY mg.sended_date DESC, mg.id DESC
LIMIT 20 OFFSET -20