Sum value on non grouped saved search

I'm trying to get the sum of a child record column without doing any grouping on the saved search. Grouping would be easier but in this case I only have control over the saved search, not the 3rd party code that uses the saved search. So I can add columns but I can't change the saved search to a grouped search.

Here's some example data...

Table A
internalid
1
2

Table B
internalid, TableAId, Amount
1, 1, 2
2, 1, 4
3, 2, 3
4, 3, 5

I'm searching Table A and I want to return the 2 rows from Table A with the total amounts from Table B.
internalid, Summed Amount
1, 6
2, 8

This is what I get however. The totals are correct but it's still returning a result row for every row in Table B.