Find the difference between 2 rows (date - same column)

Hi,
I have a table with two columns ID and mydate date type. I need to calculate the difference (number of days) difference between first row date to second and second to third and so on...)
how this can be achieved?

ID mydate DIFF_DAYS
1 01-JAN-13 0
2 05-JAN-13 4
3 14-JAN-13 9
4 15-JAN-13 1

Thanks.

So you have a table with two rows for every ID?

Code:

---

ID mydate
1 01-JAN-13
1 01-JAN-12
2 05-JAN-13
2 05-JAN-12
3 14-JAN-13
3 14-JAN-12
4 15-JAN-13
4 15-JAN-12

---

Code:

---

SELECT ID, MAX(mydate)-MIN(mydate)
  FROM mytable
 GROUP BY ID
 ORDER BY 1;

---

If you want to compare each id to the next id, for example compare 1 to 2 and 2 to 3, etc.
Then you need to use analytics with the lead/lag function.

Thank you.