SELECT project_start_date , End_Date as project_end_date 
FROM
(
select Connect_by_root Start_Date AS project_start_date , End_Date , connect_by_isleaf as is_leaf
from Projects
START WITH Start_Date NOT IN (SELECT End_Date FROM Projects)
connect by Start_Date = prior End_Date
)  
where is_leaf = 1
order by End_Date - project_start_date asc ,project_start_date asc ;