Excel sumif with criteria

Question

I have a last_name, first_name, salary, and total_salary columns. The sales person appears multiple times throughout the spread sheet. What I would like to do is write a function that will sum up the salary column in the total_salary column only where the sales person appears.

Example output:

Desired output:

Thanks

Answer 1

Try this (assuming your data is in columns A:C starting row 1):

=SUMPRODUCT(--(A1=A:A),--(B1=B:B),C:C)

Autofit down the list as required.