-- Posts with self-answers that have fewer than average other answers

select top 10 count(q.Id) as count
from Posts q
join Users u on q.OwnerUserId = u.Id
join Posts sa on q.Id = sa.ParentId and q.OwnerUserId = sa.OwnerUserId
join Posts a on q.Id = a.ParentId and q.OwnerUserId != a.OwnerUserId
inner join (select DATEDIFF(
        HOUR,
        MIN(sa.CreationDate)
         ,
        MIN(a.CreationDate)
        ) as diffdate, sa.ParentId from  ???) D on D.ParentId = q.Id
group by D.diffdate
order by D.diffdate