SUM(DISTINCT) Based on Other Columns

Question

I currently have a table that looks something like this:

+------+-------+------------+------------+
| id   | rate  | first_name | last_name  |
+------+-----         


        

Answer 1

David said he found his answer as such:

SELECT SUM(rate) FROM (SELECT * FROM records GROUP BY last_name, first_name) T1

But when you do the GROUP BY in the inner query, I think you have to use aggregate functions in your SELECT. So, I think the answer is more like:

SELECT SUM(rate) FROM (SELECT MAX(rate) AS rate FROM records GROUP BY last_name, first_name) T1

I picked MAX() to pick only one "rate" for a "last_name, first_name" combination but MIN() should work the same, assuming that the "last_name, first_name" always leads us to the same "rate" even when it happens multiple times in the table. This seems to be David's original assumption - that for a unique name we want to grab the rate only once because we know it will be the same.