sql Row_Number function is not working after created in table - sql

Question

I hope this isn't a repeated discussion. I did search through the forums and didn't find anything that related to my problem. I love this site by the way. It has helped me for a couple years now and I usually will get all my questions solved by searching this site.
Anyway, I am running into an issue in SQL with the ROW_NUMBER() function. I created a view that involves joining a different view and a table and in the view I pulled fields from both the view and the table, but I also created two fields that was a ROW_Number() field called seq_number and another field called seq_alpha.
Seq Number field is:
ROW_NUMBER() over(order by book_date, room, start) as seq_number,
The seq_alpha field is a case field that is based on what the row number is to give an alpha letter instead.
For example
case ROW_NUMBER() over(order by book_date, Room, Start)
when 1 then 'A'
when 2 then 'B'
when 3 then 'C'
....
End as seq_alpha
When I created the view for testing purposes I used a WHERE clause and everything worked exactly the way it should. I then commented out the Where clause and had the table created.
Then after the view was created I tried to pull the created view and used the same Where clause that worked when creating the view but now did it like:
select *
from created_view
where (same as I used for testing)
But now what happens is the seq_number field looks at the entire view instead of letting the where clause filter out the results. All the other data pulls correctly, but the seq_number and seq_alpha fields don't. So instead of having the seq number be 1-22 in my 22 results it is 400,000 range and the seq_alpha field doesn't even display anything because I only went up to 51 in my case.
Has anyone had similar issues with trying to pull a row_number field after it is created and the field not filtering the results with the where clause?
Thanks for your help in advance!
EDIT
After Mikael's response it seems unlikely that I am able to create a row_number field in a view and then query the view afterward and have it work the way I want. So, my next question is is there a way to create an alpha sequence based on the row number that I can put in a view and be able to query later and be able to have it work correct based on the where clause? Or do I just need to create the alpha sequence field every time I would pull this view?
J

Answer 1

row_number() enumerates the rows it sees when it is executed after the where clause is applied.
This will enumerate the whole table
select ID,
row_number() over(order by ID) as rn
from YourTable
and this will enumerate all rows where ID < 10
select ID,
row_number() over(order by ID) as rn
from YourTable
where ID < 10
If you create a view that queries the whole table
create view ViewYourTable as
select ID,
row_number() over(order by ID) as rn
from YourTable
and then query the view with a where clause ID < 10
select T.*
from ViewYourTable as T
where T.ID < 10
you are doing the same as if you used a derived table.
select T.*
from (
select ID,
row_number() over(order by ID) as rn
from YourTable
) as T
where T.ID < 10
The where clause is applied after the rows are enumerated.