Tom.Thomson (10/14/2010)
"can be used on range queries" really means "make things which are used close together live close together in the index" which, in an OLTP system, may have nothing to do with range queries (for example if I have a small numer of interactive users and a system where menus are constructed from text in a database, it's a good idea to cluster on language - if someone's using French menus he or she will probably continue to do so, and having the same text in 104 languages in cache just because it's been pulled in in French isn't useful: there's no range query involved there); the same text example blows away the "high degree of uniqueness" guideline (if it said "sets of columns" which had that property it would be sound, but it says "coumns" not "sets of columns"). The statement about identity columns is just plain false (duplicates can and do occur if uniqueness is not enforced by a constraint).
I have made this point (far less well) several times on another forum. I have promised several times to write some proof but never have. I think this is the first time I have read someone express the same opinion\truth\ignorant nonsense**
** delete according to your brigade allegiance.