Drupal Feed importers: Update Node values without needing to include all values in Feed Currently when I try to import data through a feed, importer, if any field from the mappings is missing then the data for that field gets overwritten. This is despite of selecting


  Update existing nodes


or


  Replace existing nodes


Thus how can I ensure the data does not get overwritten with blank even though those mappings are provided but the column is not included in the csv.

Thanks.
You want to stick with the Update existing nodes to retain your existing content fields here.

The simplest way to prevent overwriting is to remove whatever mappings that aren't available in your CSV. If you have different CSVs with different available columns, cloning your current CSV feed importer and remove the columns from the new importer should accommodate different data update sources.