There is no concept of that in DataTables core at the mount - the sort applies to the full data set, not a subset. If you do want to sort only a subset, then you would need to create a sorting plug-in. Its not something I've done before I'm afraid (a subset sorting plug-in!) but it should be possible with all the information available. It might involve a fairly good understand of how DataTables sorts data - specifically the aiDisplay and aiDisplayMaster arrays. I'd suggest looking at the source for _fnSort in DataTables.