create a column based on dates from different rows

[#1]

Hello!

Any ideas on how to make a table based on a criteria (end date (row 1) - start date(row 2)) for when "consecutive" dates belongs to a the new period. The periods belongs to a certain person.

Person	Start_date	End_date	Period
A	2010-01-01	2010-01-02	1
A	2010-01-03	2010-01-04	2
A	2010-01-10	2010-01-10	3
Person	Person	Start_date	Old period	Period
A	2010-01-01	2010-01-02	1	1
A	2010-01-03	2010-01-04	2	1
A	2010-01-10	2010-01-10	3	2

Kind Regards,

Markus