Cumulative count in Grafana graph


I have a PostgreSQL database connected to my Grafana dashboard. I’d like to make a cumulative count and show it in a graph, but I haven’t found the way to achieve it. Concretely, my table looks like this:

project_name / project_namespace / project_creation_date
Project A / Namespace A / 2019-05-22
Project B / Namespace B / 2019-05-23
Project A2 / Namespace A / 2019-05-23
Project C / Namespace C / 2019-05-23
Project D / Namespace D / 2019-05-24
Project B2 / Namespace B / 2019-05-24

What I’d like to show in my graph is, for each date, the number of namespaces existing. For May 22nd there is one namespace (A), for May 23rd there are two new namespaces (B and C), and for May 24th a new one (D). This way, the cumulative evolution of namespaces is this:

2019-05-22 Number of namespaces: 1 (A)
2019-05-23 Number of namespaces: 3 (A, that already existed, and new B and C)
2019-05-24 Number of namespaces: 4 (A, B and C, that already existed, and D)

This way, the graph should mark 1 in 22nd, 3 in 23rd and 4 in 24th. How could I achieve this with a SQL sentence in Grafana?

Very grateful for your help,