First off, this question should be posted in
Microsoft.public.sqlserver.programming. Clustering is a technology which
allows individual computers to share the same data and back each other up to
prevent system failures. Clients connect to a virtual server, whose
resources float between nodes which form the cluster.

Clustered indexes are when the data is clustered or grouped in a predefined
format or order for rapid retrieval of ranges of data.

16 columns makes your index very large and I suspect inefficient. You may be
able to use an indexed view to group your data in different orders for your
particular usage. And yes, clustered indexes only support a maximum of 16
columns or keys in SQL 200x.

Yes.  Why are you trying to create an index with 21 columns in it?  That is
quite a bit beyond overkill.

Hi

Wrong newsgroup, crossposted to microsoft.public.sqlserver.programming

Why would you want to create a compound index of 16 or more columns? Your
query has to be very specific to be able to use it and the overhead
maintaining it will be high too.

If you have a table, with columns A-Z and you build and index on A, B, C, D
(in that column sequence), a where clause on A, B, C could use the index, a
query on column B can't, neither can a query on C, D. Column A always has to
be involved as it is the 1st sort sequence for the column.

Maybe the DB design is not optimal if you need to go to such extremes.

Regards
--------------------------------
Mike Epprecht, Microsoft SQL Server MVP
Zurich, Switzerland

IM: mike@epprecht.net

MVP Program: http://www.microsoft.com/mvp

Blog: http://www.msmvps.com/epprecht/