In Journey Builder, I want to check if my Contact has a Device Id or not so I can send a mobile push notification. I'm using Contact Data --> MobilePush Data --> MobilePush Demographics --> Device Id (as shown below)
Now the question is, how will my Subscriber in my Entry Source DE connected to the MobilePush Demographics. For this, I'm trying to connect the DE with Contact in Contact Builder. However, I cannot find ContactKey in Contacts to link to the SubscriberKey in the DE. I only see ContactId, which doesn't help much.
How to link ContactKey to the Journey Entry DE for MobilePush Demographics?
Similarly for Mobile Connect as well.