Walter,
My understanding of an non-clustered index scan is that any efficiency improvement comes from its containment of indexed data separately from the rest of the row. It still has to scan the content for each potential candidate, doesn't it, albeit in a more concise form? And isn't it true that sometimes it may be quicker to do a full scan- e.g. if there are lots of non-discriminatory where clauses...
surname like %m% and firstname like %w% and town like %c% and street like %e%
"... They ne'er cared for us
yet: suffer us to famish, and their store-houses
crammed with grain; make edicts for usury, to
support usurers; repeal daily any wholesome act
established against the rich, and provide more
piercing statutes daily, to chain up and restrain
the poor. If the wars eat us not up, they will; and
there's all the love they bear us."
-- Shakespeare: Coriolanus, Act 1, scene 1
