Need help urgently, have to compare dates between 2 rows in one table

Originally Posted by site

Have to compare dates of two rows in one table
Input table
COL1| COL2| COL3| COL4
1| A| 1-Jan-07| 6-Feb-08
2| A| 7-Feb-08| 31-Mar-08
3| A| 1-Jan-09| NULL

SQL code to compare COL 4 date (Row 1) with COL 3 date (row 2)
and compare COL 4 date (Row 2) with COL 3 date (row 3)

If COL3 (ROW2) date is equal to COL 4 (ROW 1) + 1 = output Col 4 =A
If COL3(ROW2) date is equal to COL 4 (ROW 1) + 2 = output Col 4 =R


OUTPUT table
COL1| COL2| COL3| COL4
A| 1-Jan-07|| 6-Feb-08| A
A| 7-Feb-08| 31-Mar-08| O
A| 1-Jan-09| NULL| R