google cloud platform – Solution for Joining BigQuery tables (streaming)

For your requirement, you can consider using Scheduled Queries by incrementally updating the data to the new table. You need to create a Scheduled Query and configure it to append the data of the 3 tables to the new table and further set the interval of time to auto update the query.

You can also try creating Materialized View for better query performance. Create a Materialized view that automatically refreshes the data of the 3 tables to the new table within the certain interval of time provided.