Q&A for spacecraft operators, scientists, engineers, and enthusiasts
select u.DisplayName from users u where (select count(*) from posts p where p.CreationDate between '2010/01/01' and '2010/12/21' and p.OwnerUserId=u.id)=0 and (select count(*) from posts p where p.CreationDate between '2015/01/01' and '2015/12/31' and p.OwnerUserId=u.id)>0