Building an Oracle view with a sequence - oracle

Question

I'm trying to build a new Oracle view off of a table. The only difference between the two is that I want to add a new column with a unique ID. The IDs have to be unique, but does not need to be ordered.
I tried to run a script like this:
CREATE VIEW <VIEW_NAME>
(
ID, VALUE1, VALUE2,...
)
AS
SELECT SEQ1.NEXTVAL, VAL1, VAL2,... FROM <TABLE>
However, I'm running into errors. A previous post mentions it's not really possible but didn't elaborate so I was hoping to get some clarity. Doing an INSERT doesn't seem useful because I'd have to populate all the other values too, at least from what I've been reading.
Edit: IDs should be consistent every time I look at the view.
Picture of error:

Answer 1

If you just want a unique value for each row then you can use ROWNUM or the ROW_NUMBER analytic function:
CREATE VIEW view_name ( ID, VALUE1, VALUE2,... ) AS
SELECT ROWNUM,
VAL1,
VAL2,
...
FROM table_name
or
CREATE VIEW view_name ( ID, VALUE1, VALUE2,... ) AS
SELECT ROW_NUMBER() OVER ( ORDER BY val1, val2 ),
VAL1,
VAL2,
...
FROM table_name
IDs should be consistent every time I look at the view.
I do not think this is possible; you would need to store the IDs somewhere and that requires a table rather than a view/sequence.
For example:
Oracle Setup:
CREATE TABLE table_name ( val1, val2 ) AS
SELECT 1, 'a' FROM DUAL UNION ALL
SELECT 2, 'b' FROM DUAL
CREATE SEQUENCE view_name__seq;
CREATE FUNCTION seq_value RETURN NUMBER
IS
BEGIN
RETURN view_name__seq.NEXTVAL;
END;
/
CREATE VIEW view_name ( id, value1, value2 ) AS
SELECT seq_value, val1, val2 FROM table_name;
If you select from the view then first time:
SELECT * FROM view_name;
you get:
ID | VALUE1 | VALUE2
-: | -----: | :-----
1 | 1 | a
2 | 2 | b
and second time you get:
ID | VALUE1 | VALUE2
-: | -----: | :-----
3 | 1 | a
4 | 2 | b
db<>fiddle here
and the IDs are not consistent.

Answer 2

I would suggest you to use INVISIBLE column in your base table.
ALTER TABLE MY_TABLE ADD MY_UNIQUE_ID NUMBER INVISIBLE;
Now, assign sequential number to it or use as GENERATED AS IDENTITY (try this)
This will not break you application and you can use it in your view to achieve the desired result and return consistent values in your view.
Cheers!!