OK I have added a relation to an existing DataObject with records. The relation is displayed in the CMS through a DropdownField.
I have set the default value for this relation for new records using populateDefaults(), say to 3.
The problem I am having how would I change the default value for records that existed before I added this relationship (as they show up as blank in the GridField and with an ID of 0 in the database for the relationID column).
I can edit the database directly and update all records with ID 0 but an solution coded in the dataobject would be preferable, if this is possible? I also don't want to ask my editors to re-save all records one by one.