Copying down results from an ARRAY

I'm having issues with joining together separate tables what don't have anything in common. Essentially, I have a table with all possible customer IDs and a separate table for all possible dateweek ranges. I want to join them together in order to use at a later time to find date ranges for customer IDs where they are null in another dataset.

SELECT customer_id, ARRAY( SELECT DISTINCT CONCAT(year,week) AS yearweek FROM sales) FROM customers

While this works, I need to get the customer IDs to copy down in order to use it as a JOIN later on.

In the end, I want it to look like this: