Edit/Update and Delete Operations on Table without Primary Keys not Supported using RecordSet

[Samba143]

I am using CRecordset (MFC) to perform Edit/Update and Delete operations on table which doesn't have Primary key.
I get error saying "incompatible rowset"

For quick reference, I tried the same scenario against MS Access using Access driver and everything works fine.

Could you please clarify why Update and Deletes can't be supported on tables having no PKs?