Reset external ID to null

Question

We frequently try to match facebook event attendees to contacts in our database in order to send targeted emails to the person. By matching them to our database we know a lot more about the people (e.g. geolocation to include reference to an elected representative). The process in civi to do this is cumbersome. We take the list of people from facebook (names only) and assign an external ID, then import the list to civi. We assume that names are unique (a somewhat reasonable assumption for our database). Following this process we want to free up the contact's external ID field to allow the next import to run without having to manually de-dupe anyone who has an external ID previously set. How can we either:

1. Do this without external IDs

2. Reset the external ID to null

We are using wordpress 4.4.1 and civi 4.6.10

Answer 1

If you have sql access, it's a very simple update query

update civicrm_contact c
set    c.external_identifier = null
where  c.external_identifier is not null

This, of course, will null all of them for all contacts but I think that is what you're asking for.

Answer 2

You could do a batch update via profiles see CiviCRM user and administrator guide.

I just tried it and it only took a couple of minutes to set the profile up. You only need one field for External Contact Id. In a nutshell, once you set up the profile, you query up the contacts you wish to change, select Batch Update via Profile, select the profile. Then you can null out the first record click on the copy icon and it nulls out all the rest.

One caveat is you can only batch update one contact type at a time so you if you have both households and individuals you'll need to do the query twice.