Can I create clustered index on columns having dupliacte data. If I can, how does it work

Yes, you can. It is not going to be unique thought. Make sure that data
selectivity is such as index would be used by you typical query(s). Look at
the query plan for "index seek" or compare execution cost. As far as I read,
if index is not specified as unique SQL Server creates an additional
internal identifier to make a value unique.

Ilya

[quoted text, click to view]