I am trying to figure out the total amount of donations by each individual
donor during last year. My spreadsheet records each gift on a separate line.
Some donors have given once, others as much as 12 times. How can I create a
formula that gives the sum of donation by each individual? Is sumif the
correct formula to use?
My spreadsheet has over 7000 rows!

I've tried this formula =SUMIFS(O3:O7,D3:D7,"=*") (I've only tried a small
range to test my formula)
O3 to O7 is the column and range for the donation amount
D3 to D7 is the last name column
and "=*" was my attempt to condition the sum on similar last names.

Because I have several donors with the same last name, would it be better to
use their unique donor ID# to be a condition?

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Thank you,
Tom Ferrin