But setting up slave db to mirror a master copy may not work either. I figure that the Man wants only portions of the master being replicated. Further, data boundaries are determined by user priviledges. That is, he doesn't simply want to copy table C and leave tables A and B on the main server. It seems like they want to copy portions of various tables.
But you are right, this is a dangerous path. My best bet would be to definitely create multiple database groups and tablespaces (for Oracle) or separate databases (for MySQL). Have certain cgi scripts run as user Z who's only allowed to access database X. Appears pretty secure to me! :).
Well, the contractor could always ditch the project and search for greener (sane) pastures ;-)
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# Under Construction