sql function to add each row values - sql

Question

table a
id
1
2
3
4
i want output to be like this:
id id_new
1 1
2 3
3 6
4 10
basically we are adding row values of a column in each row
i.E 2=1+2 ,3=1+2+3 and so on
you can use any cursor,function or query

Answer 1

You seem to want a cumulative sum. The ANSI standard function is a window function, supported by Oracle:
select id, sum(id) over (order by id) as id_new
from t;
It seems strange to do this with a column called id, though. Usually, cumulative sums are on counts or amounts or something measurable.
If you need to actually update the data, then you can use a correlated subquery:
update t
set id_new = (select sum(id) from t t2 where t2.id <= t.id);
This will work on a small table. For anything larger, use merge.

Answer 2

The comment by Pradeep is probably the way to go on Oracle. But there is an alternative to that, which is using a correlated subquery to compute the rolling sum:
SELECT
id,
(SELECT SUM(t2.id) FROM yourTable t2 WHERE t2.id <= t1.id) id_new
FROM yourTable t1;
This answer may have some merit because not every database supports analytic functions. And even if we are using Oracle in the context of, e.g., a Java application, an ORM interface like JPA or Hibernate may not support analytic functions.

Answer 3

Piece of cake.
SQL> with test (id) as
2 (select 1 from dual union
3 select 2 from dual union
4 select 3 from dual union
5 select 4 from dual
6 )
7 select id, sum(id) over (order by id) id_new
8 from test
9 order by id;
ID ID_NEW
---------- ----------
1 1
2 3
3 6
4 10
SQL>
[EDIT, a generalized option]
SQL> select level id, sum(level) over (order by level) new_Id
2 from dual
3 connect by level <= &n;
Enter value for n: 5
old 3: connect by level <= &n
new 3: connect by level <= 5
ID NEW_ID
---------- ----------
1 1
2 3
3 6
4 10
5 15
SQL> /
Enter value for n: 3
old 3: connect by level <= &n
new 3: connect by level <= 3
ID NEW_ID
---------- ----------
1 1
2 3
3 6
SQL>