Query on dates - Thanks

Question

Hello,
I need some help in writing a query. Any suggestions are greatly appreciated.
Below is a table which has start and end_dates for each person's record. Each record of a person should have an end date(except the latest record of every person) which should be one less than the start-date of the next record. Some of the records of the person are missing. I need to write a query to find the records which doesn't have the end date and the expected end date for that record.
Thank you in advance.
KK
PERSON_ID
START_DATE
END_DATE
111
9/1/2005
111
12/1/2004
8/31/2005
111
9/1/2004
111
9/1/2003
8/31/2004
111
12/30/2002
8/31/2003
137
9/1/2012
137
9/1/2011
8/30/2012
137
9/1/2010
8/31/2011
137
9/1/2009
8/31/2010
137
9/1/2008
8/31/2009
137
9/1/2007
8/31/2008
137
9/1/2006
8/31/2007
137
9/1/2005
8/31/2006
137
9/1/2004
8/31/2005
137
10/24/2003
8/31/2004
137
9/1/2003
137
12/30/2002
8/31/2003
148
9/1/2011
148
9/1/2010
8/31/2011
148
9/1/2009
8/31/2010
148
9/1/2008
8/31/2009
148
9/1/2007
8/31/2008
148
9/1/2006
8/31/2007
148
9/1/2005
8/31/2006
148
4/8/2005
8/31/2005
148
9/1/2004
148
9/1/2003
8/31/2004
148
12/30/2002
8/31/2003

Answer 1

sounds like a job for lead, something like:
select t.*
     , lead(start_date) over(partition by person_id order by start_date) - 1 end_date_calculated
  from t
order by start_date;
PERSON_ID START_DATE END_DATE   END_DATE_C
       111 30.12.2002 31.08.2003 31.08.2003
       111 01.09.2003 31.08.2004 31.08.2004
       111 01.09.2004            30.11.2004
       111 01.12.2004 31.08.2005 31.08.2005
       111 01.09.2005
If the column generated with lead is null, then it is the last row for the given person_id.