简单通用方法：

select
coalesce(crte.creationdate, cmpl.CompletionDate) as theDate,
crte.cnt as created,
cmpl.cnt as completed
from
(select creationdate, count (*) as cnt from vOKPI_Tickets where creationdate  is not null group by creationdate) crte
full join
(select CompletionDate, count (*) as cnt from vOKPI_Tickets where CompletionDate  is not null group by CompletionDate) cmpl
on crte.creationdate  = cmpl.CompletionDate

可以取消拆分和聚合。一般方法是：

select dte, sum(created), sum(completed)
from ((select creationdate as dte, 1 as created, 0 as completed
       from vOKPI_Tickets
      ) union all
      (select completed as dte, 0  created, 1 as completed
       from vOKPI_Tickets
      ) 
     ) t
group by dte;

在sql server中，可以使用 cross apply 为此：

select d.dt, sum(d.is_completed) count_created, sum(d.is_completed) count_completed
from vokpi_tickets t
cross apply (values (creationdate, 1, 0), (completion_date, 0, 1)) as d(dt, is_created, is_completed)
where d.dt is not null
group by d.dt