Loads data from a data source into Salesforce, where existing records with a matching custom external ID field are updated; records without matches are inserted as new records.

If you are performing an upsert:

1. Your CSV file must contain a column of ID values for matching against existing records. The column may be either an external ID (a custom field with the “External ID” attribute), or Id (the Salesforce record ID). From the drop-down list, select which field to use for matching. If the object has no external ID fields, Id is automatically used. For more information on external IDs, see “Custom Field Attributes” in the online help. Click Next to continue.
2. If your file includes the external IDs of an object that has a relationship to your chosen object, enable that external ID for record matching by selecting its name from the drop-down list. If you make no selection here, you can use the related object’s Id field for matching by mapping it in the next step. Click Next to continue.