Oracle 18c

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create table table_b(
	id int, 
	table_a_id int, 
	"order" int, 
	label_x varchar(1),
	label_y varchar(1),
	value int
);
begin
insert into table_b values(1, 1, 1, 'A', 'B', 1);
insert into table_b values(2, 1, 2, 'B', 'C', 2);
insert into table_b values(3, 1, 3, 'C', 'D', 3);
insert into table_b values(4, 1, 4, 'D', 'E', 4);
insert into table_b values(5, 1, 5, 'E', 'F', 5);
end;
/
1 rows affected

select 
	t1.table_a_id,
	t1.label_x,
	t2.label_y,
	sum(t2.value) over(
		partition by t1.table_a_id, t1.label_x
		order by t1."order", t2."order"
	) agg_value
from 
table_b t1
inner join table_b t2 
	on  t1.table_a_id = t2.table_a_id
	and t2."order" >= t1."order"
order by t1."order", t2."order"


TABLE_A_ID
LABEL_X
LABEL_Y
AGG_VALUE


1
A
B
1

1
A
C
3

1
A
D
6

1
A
E
10

1
A
F
15

1
B
C
2

1
B
D
5

1
B
E
9

1
B
F
14

1
C
D
3

1
C
E
7

1
C
F
12

1
D
E
4

1
D
F
9

1
E
F
5

TABLE_A_ID	LABEL_X	LABEL_Y	AGG_VALUE
1	A	B	1
1	A	C	3
1	A	D	6
1	A	E	10
1	A	F	15
1	B	C	2
1	B	D	5
1	B	E	9
1	B	F	14
1	C	D	3
1	C	E	7
1	C	F	12
1	D	E	4
1	D	F	9
1	E	F	5

TABLE_A_ID	LABEL_X	LABEL_Y	AGG_VALUE
1	A	B	1
1	A	C	3
1	A	D	6
1	A	E	10
1	A	F	15
1	B	C	2
1	B	D	5
1	B	E	9
1	B	F	14
1	C	D	3
1	C	E	7
1	C	F	12
1	D	E	4
1	D	F	9
1	E	F	5

TABLE_A_ID	LABEL_X	LABEL_Y	AGG_VALUE
1	A	B	1
1	A	C	3
1	A	D	6
1	A	E	10
1	A	F	15
1	B	C	2
1	B	D	5
1	B	E	9
1	B	F	14
1	C	D	3
1	C	E	7
1	C	F	12
1	D	E	4
1	D	F	9
1	E	F	5