ID NUM
---------- ----------
1 50
2 80
3 100
4 100
SQL> select a.*
2 from
3 t1 a,
4 (select id, last_id
5 from (select id, lag(id) over(order by id) last_id, num, lag(num) over(order by id) last_num
from t1)
6 where num + last_num > 150 and rownum = 1
7 ) b
8 where a.id = b.id
9 or a.id = b.last_id;