merge DATE-rows if episodes are in direct succession or overlapping

Question

I have a table like this:

ID    BEGIN    END

If there are overlapping episodes for the same ID (like 2000-01-01 - 2001-1

Answer 1

I'm not making full sense of your question, but I'm absolutely certain that you need to look into the lead()/lag() window functions.

Something like this, for instance, will be a good starting point to place in a subquery or a common table expression, in order to identify whether rows overlap or not per id:

select id,
       lag(start) over w as prev_start,
       lag(end) over w as prev_end,
       start,
       end,
       lead(start) over w as next_start,
       lead(end) over w as next_end
from yourtable
window w as (
       partition by id
       order by start, end
       )