Is it possible to have a table column summarizing columns from other tables?

Hi everyone,

Just wondering if anyone has a solution to the following scenario I have:

I want to have multiple database tables e.g.

Table 1

mortgage payments

etc

Table 2

Water bills

And then a table 3

1. mortgage payments sum
2. water bills sum

So overall I want to be able to get the sum from each of Table 1 and 2 and have that summarized in a column in Table 3.

Is this possible at all? Or is there an alternative that achieves anything similar?

Thanks