Cannot create indexed view because it contains one or more UNION, INTERSECT, or EXCEPT operators. Consider creating a separate indexed view for each query that is an input to the UNION, INTERSECT, or EXCEPT operators of the original view.
This error occurs when you try to create an index on a view that contains a UNION, INTERSECT, or EXCEPT operator. For example: the following statement will raise the above error.
You cannot create an index on a view that makes use of a union operator. Really no way around that, sorry!
I would imagine you’ve seen this, but check out this MSDN page. It gives the requirements for indexed views and explains what they are and how they work.
As to whether or not you’d see a performance benefit if you COULD index the view, that would depend entirely on the size of your tables. I would not expect any impact on creating separate indexed views, as I would assume that your tables are already indexed and you aren’t doing any joining or logic in the view.
Creating Indexed Views