We have a database with invoices from different clients with the date that the invoice was created.
We now want to calculate a cumulative count of the invoices for each customer. Invoice 1 of customer X should show in a new column "1", Invoice 2 of customer X "2" and so on. For the next customer it should start again from "1".
Which formulas can we use for this problem?
| Client | Created on | Cumulative count |
|---|---|---|
| 1 | mar-14 | 1 |
| 1 | jun-15 | 2 |
| 1 | dec-16 | 3 |
| 2 | feb-14 | 1 |
| ... | ... | 2 |