[SQL] Intersection of two date interval

[Suha Onay]

Hi,

How can i find the number of days in the intersection of 2 date interval?
For example:
1st  interval: (10.01.2007, 20.01.2007)
2nd interval: (13.01.2007, 21.01.2007)
The intersection dates are: 13,14,15,16,17,18,19, 20
The result is: 8

How can i find the result, 8 in an sql query without using CASE statements?

Table columns are id PK, date1 date, date2 date.

Thanks for all your help.


Suha