SQL Server Convert datetime to date without null

Yes the reason it is showing Nullable for not nullable column is because you are making your outer select as computed based on isnull condition and others.

In this table Email is not nullable column and now if I give Isnull condition in inner query it will be like this.

Now if I don't give any condition it will be like this.

You can refer to this link as well for detailed explanation.

https://dba.stackexchange.com/questions/114260/why-is-a-not-null-computed-column-considered-nullable-in-a-view