Oracle 18c

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create table a_test_table (id number(4,0), cost number(15,2), priority number(4,0)) ;
insert all
  into a_test_table (id, cost, priority) values (1, 1000000, 10)
  into a_test_table (id, cost, priority) values (2, 10000000, 9)
  into a_test_table (id, cost, priority) values (3, 5000000, 8)
  into a_test_table (id, cost, priority) values (4, 19000000, 7)
  into a_test_table (id, cost, priority) values (5, 20000000, 6)
  into a_test_table (id, cost, priority) values (6, 15000000, 5)
  into a_test_table (id, cost, priority) values (7, 2000000, 4)
  into a_test_table (id, cost, priority) values (8, 3000000, 3)
  into a_test_table (id, cost, priority) values (9, 3000000, 2)
  into a_test_table (id, cost, priority) values (10, 8000000, 1)
select 1 from dual ;
10 rows affected

select * from a_test_table ;


ID
COST
PRIORITY


1
1000000
10

2
10000000
9

3
5000000
8

4
19000000
7

5
20000000
6

6
15000000
5

7
2000000
4

8
3000000
3

9
3000000
2

10
8000000
1


with  rt (id, cost, running_total, priority) as
(
    (
    select 
        id,
        cost,
        cost as running_total,
        priority
    from 
        a_test_table
    where cost <= 20000000 
    order by priority desc
    fetch first 1 rows only
    )
    
    union all
    
        select 
            t.id,
            t.cost,
            t.cost + rt.running_total,
            t.priority
        from a_test_table  t
             join rt 
             on t.priority < rt.priority      -- redundant but throws
                                              -- "cycle detected error" if omitted
             
             and t.priority =                             -- needed 
                 ( select max(tm.priority) from a_test_table tm
                   where tm.priority < rt.priority
                     and tm.cost + rt.running_total <= 20000000 )
    )
    select *
    from rt ;


ID
COST
RUNNING_TOTAL
PRIORITY


1
1000000
1000000
10

2
10000000
11000000
9

3
5000000
16000000
8

7
2000000
18000000
4
ID	COST	PRIORITY
1	1000000	10
2	10000000	9
3	5000000	8
4	19000000	7
5	20000000	6
6	15000000	5
7	2000000	4
8	3000000	3
9	3000000	2
10	8000000	1