identify users before and after they get their user_id

  • 10 September 2023
  • 3 replies



in my defined flow, a user gets a user_id after they sign up to the system.

Before the user signs up and gets his user_id, I can view all his events by looking at amplitude_id. 

After the user signs up, I can view all his events by looking at user_id.


my issue is that I am exporting all of Amplitude data to BigQuery, and I want to “merge” that user’s events (pre-sign up and after signup events) and can not find what is there that “unites” them. 

it's like all the user's properties are changing after he gets his user_id.

The user stream on amplitude shows the full user journey (pre-sign up and after signup events), and I  want to be able to do the same in my BQ.


thank you




3 replies

Userlevel 7
Badge +10

Hi @shani cohen 

In your BQ export, you should get the Merged User Table. Ideally, the amplitude_id and merged_amplitude_id should be sufficient to create the join condition for your use case.

Hope this helps.


Hi @Saish Redkar Thanks for your answer

I am not sure it solves my problem since I don't have a merged_amplitude_id.

I'll add more details about the scenario: 


The user enters the system, these are his properties:


The user signs up (gets his user_id), and now this is his properties:

  • he got user_I d
  • the device_id has changed
  • he got amplitude_id (this I know by looking at the BQ events table and looking for the amplitude_id that appears on the user’s page, and see I only have events that happen after the user sign-up event 



regarding your suggestion:

“the amplitude_id and merged_amplitude_id should be sufficient to create the join condition for your use case”

The problem is that I  don't have merged_id for the user (as explained in the merged_users documentation).


So the question remains, How can I connect between the pre-sign-up events and the after-signup events?

Thank you

Userlevel 7
Badge +10

If pre signup device_id is different than the device_id captured during user_id login, then I think the merge doesn’t apply in this case. There would be two different amplitude_ids assigned as far I understood this document