Given that you are relatively new to SQL, I will start off by suggesting that you change your approach. By having one table with data present, and another table with data missing, you are making this more complicated that it has to be. I recommend just maintaining a single CUSTOMERS table with all customers present. Then, if you want to find out if, e.g., a custom is missing data for V2, you may use the simple query:
SELECT *FROM CUSTOMERSWHERE V2 IS NULL;This approach frees you from having to maintain a separate table which records what is missing. If the data isn't present in CUSTOMERS, then you already know it's missing.