Case Insensitive searches

Hi all,

I need some guidance as to how best accomplish a case insensitive search while still using indexes. One thing I was wondering was does PL/SQL support regular expressions and can they be applied to existing indexes. I'm trying to avoid having to rebuild indexes forcing them to using upper case and I certainly don't want a function (ie UPPER) on the field side of the equation which would cause a table scan instead of an index search.

Also does anyone know if Oracle 9i support a switch to use case insensitive comparisons?

Thanks,

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Craig Burkett