How to Import content without affecting existing contents I have installed Data export and import

.i created nodes dataset file using above module and copied that file and pasted in another drupal site. when i import using that dataset file,it is replacing already existing contents. is it possible to import without affecting existing contents.
Looking at the modules in question it states that the purpose is "...to export data from a site into datasets. These datasets are then imported into another site in such a way that the two sites end up with EXACTLY THE SAME DATA INCLUDING ID NUMBERS."

Looking at the drush commands the module provides there are not arguments to maintain any 'current' data. It will force the state of the dataset.