new_id			id 		PARENT_ID
1			100		
2			102		100
3			103		100
4			104		102
5                       105             102


i need an update statement so that new_id will get updated to parent_id as shown below.

AFTER UPDATE I WANT THE OUTPUT AS BELOW:

new_id			id 		PARENT_ID
1			100		
2			102		1
3			103		1
4			104		2
5                       105             2