with temp as (
select *, row_number() over(order by end_date) as rn
from projects
),
temp2 as (select a.task_id
, a.start_date
, a.end_date
, b.end_date as next_end_date
, datediff(dd, b.end_date, a.end_date) datedif
, case when datediff(dd, b.end_date, a.end_date) = 1 then 0 else 1 end flag
from temp as a
left join temp as b on a.rn = b.rn+1
),
temp3 as (select *
, sum(flag) over(order by end_date) as group_id
from temp2
)
select min(start_date), max(end_date)
from temp3
group by group_id
order by datediff(dd, min(start_date), max(end_date)), min(start_date)