code: def namedb_delete_prepare( cur, primary_key, primary_key_value, table_name ):
      
      # primary key corresponds to a real column 
      namedb_assert_fields_match( cur, {primary_key: primary_key_value}, table_name, columns_match_record=False )
  
      query = "DELETE FROM %s WHERE %s = ?;" % (table_name, primary_key)
      values = (primary_key_value,)
      return (query, values)
docs: Prepare to delete a record, but make sure the fields in record
      correspond to actual columns.
      
      Return a DELETE FROM ... WHERE statement on success.
      Raise an Exception if not.
  
      DO NOT CALL THIS METHOD DIRETLY