Ask HN: In Bigquery, how to denormalize tables from different 3rd party source?

have data about contacts in Salesforce. I also have data about the contacts in Intercom/Zendesk. I want to create a denormalized table where the data in Salesforce and Intercom is both merged into a single table so I can query about the contact. Imagine, I dumped the Salesforce data into a Bigquery table. The problem is that the we might not dump Intercom/Zendesk until later. So we may only add Salesforce data into a Bigquery table now. And later we may add Intercom data. My question is how to merge these (existing data in Salesforce BQ table and new data from Intercom)? Assume that the Email is the primary key in both 3rd party sources and we can join them.

Do we need to take the Salesforce data out of the BQ table and run it through some tool to merge both tables and create a new table in BQ? What will happen if we keep getting new data in both Salesforce and Intercom?

BTW, if you could point to some simple Node.js tools, that's be great!