Can custom objects and lookup relationship fields be linked using the record external id attribute?

Question

Can custom objects and lookup relationship fields be linked using the record external id attribute?

Answer

Yes, they can. The external id attribute can be used to reference a custom object. For more information, see the API documentation: Lookup Relationships

For example, you can use an external id to link a record from a custom object based on the value entered by an end user in a ticket form.

The challenge with lookup relationship fields is that only agents can edit them. To overcome this limitation, you can use a webhook or external web service to update the Lookup field. This process involves taking the value entered in a standard text field or a drop-down field and setting it in the Lookup field, enabling updates that would otherwise be impossible.

Important: Zendesk doesn't support using webhooks for Zendesk APIs as a workaround to automatically update tickets. Doing so can result in race conditions and other conflicts. For more details, see the article: Can I use a trigger and a webhook to update tickets?

Here is a sample payload for an API call using the Tickets endpoint:

{
   "ticket":{
      "custom_fields":[
         {
            "id":FIELD_KEY, // Lookup field
            "value":"external_id:{{ticket.ticket_field_FIELD_KEY}}" // Custom field on ticket form (modified by end-user)
         }
      ]
   }
}

For more information, see the API documentation: Custom objects