most_recent_notifications_older_than some date

most_recent_notifications_older_than.sql

select v.name, max(n.inserted_at)
from variables v
         left join notifications n on v.id = n.variable_id
where tenant_id = 2
group by v.name
having max(n.inserted_at) < '2020-02-28 12:25:07.000000'
 or max(n.inserted_at) is null --disjunction clause