Why Row_Number in a view gives a nullable column - sql

Question

I have a view using a CTE and I want use a row number to simulate a key for my edmx in Visual Studio
ALTER VIEW [dbo].[ViewLstTypesArticle]
AS
WITH cte (IdTypeArticle, IdTypeArticleParent, Logo, Libelle, FullLibelle, Racine) AS
(
SELECT
f.Id AS IdTypeArticle, NULL AS IdParent,
f.Logo, f.Libelle,
CAST(f.Libelle AS varchar(MAX)) AS Expr1,
f.Id AS Racine
FROM
dbo.ArticleType AS f
LEFT OUTER JOIN
dbo.ArticleTypeParent AS p ON p.IdTypeArticle = f.Id
WHERE
(p.IdTypeArticleParent IS NULL)
AND (f.Affichable = 1)
UNION ALL
SELECT
f.Id AS IdTypeArticle, p.IdTypeArticleParent,
f.Logo, f.Libelle,
CAST(parent.Libelle + ' / ' + f.Libelle AS varchar(MAX)) AS Expr1,
parent.Racine
FROM
dbo.ArticleTypeParent AS p
INNER JOIN
cte AS parent ON p.IdTypeArticleParent = parent.IdTypeArticle
INNER JOIN
dbo.ArticleType AS f ON f.Id = p.IdTypeArticle
)
SELECT
*,
ROW_NUMBER() OVER (ORDER BY FullLibelle) AS Id
FROM
(SELECT
IdTypeArticle, IdTypeArticleParent, Logo, Libelle,
FullLibelle, Racine
FROM cte) AS CTE1
When I look in properties of column I see Id bigint ... NULL
And my edmx exclude this view cause don't find a column can be used to key
When I execute my view ID have no null. I've all my row number.
If someone encounter this problem and resolved it ... Thanks

Answer 1

SQL Server generally thinks that columns are NULL-able in views (and when using SELECT INTO).
You can convince SQL Server that this is not the case by using ISNULL():
select *,
ISNULL(ROW_NUMBER() over(ORDER BY FullLibelle), 0) as Id
from . . .
Note: This works with ISNULL() but not with COALESCE() which otherwise has very similar functionality.