sql - Comparing consecutive rows using oracle -

i have table looks this:

| id | from_date | to_date | ------------------------------ | 1  |  1/1/2001 | 2/1/2001| | 1  |  2/1/2001 | 3/1/2001| | 1  |  2/1/2001 | 6/1/2001| | 1  |  3/1/2001 | 4/1/2001| | 2  |  1/1/2001 | 2/1/2001| | 2  |  1/1/2001 | 6/1/2001| | 2  |  2/1/2001 | 3/1/2001| | 2  |  3/1/2001 | 4/1/2001| 

it sorted id, from_date, to_date.

what want delete rows from_date earlier to_date previous line , id equal id previous line. in example, delete 3rd , 6th rows only.

i know need kind of looping structure accomplish this, don't know how since i'm looking @ 2 rows @ time here. how can accomplish within oracle?

edit: using 'lag' function quicker , easier, end deleting 4th , 7th rows - not want do. example, when gets row 4, should compare 'from_date' 'to_date' row 2 (instead of row 3, because row 3 should deleted).

you use lag window function identify these rows:

delete mytable rowid in (select rowid                   (select rowid, from_date,                                 lag(to_date) on                                    (partition id                                    order from_date, to_date)                                    lag_to_date                           my_table) t                  from_date < lag_to_date)