Q5_m

select start_date, min(end_date)
from 
    -- choose start dates that are not end dates of other projects, this way we get start dates       of each unique projects
    (select start_date from projects where start_date not in (select end_date from projects)) s,
    -- same logic, choose end dates that are not start dates of other projects, this way we get         end dates of each unique projects
    (select end_date from projects where end_date not in (select start_date from projects)) e
    -- choosing min ensures that for each start date we pick the next minimun consecutive end date
where start_date < end_date
group by start_date
order by datediff(min(end_date), start_date) asc, start_date asc;