New v/s Existing customer split

[ayushmittal22]

Hi, I have customer_ids in my data and I want to find out how what % of the total customer ids were present in the data before this month and how many are unique to this month. 

With this, I want to find out the percentage % split between New v/s Existing Customers month on month. 

For ex- Out of 100 ids, 45 were present in previous months' data and 55% are unique to this month. 

I would do it manually on Excel, but rows are >4 million.

How can I do it? Please help!!

 @amitchandak @Greg_Deckler @Jihwan_Kim 

[visheshjain · Accepted solution]

Hi @ayushmittal22,

I would approach the problem something like this:

1. Get a virutal table of customers who have sale >0 before the current month.

2. Get another virtual table of the customers who have sale >0 in the current month.

3. Use the EXCEPT() function between both the virtual tables, leaving only the new customers in the current month.

4. Count the rows of the table obtained in the previous step.

5. Divide this number by the total number of unique customers until the last sale date.

Hope this helps.

Thank you,

Vishesh Jain