How to create an index view?
Some thoughts...


what filters or joins will you use on the view? These determine what indexes you'll need on the table
have you considered a computed column to pre-sum cola+colb at the table level?


Personally, I avoid views because a view doesn't have persistence (unless it is indexed itself): it is simply a macro expanded by the query optimiser. That is, say you have 2 views that join (one with 3 table, one with 4 tables): the actual query plan will show all 7 tables.

In the case above, you have no filters. This means that no index can help you: you'll get a clustered index (which is actually the table and you do have a clustered index, right?) scan