I have a large database and am putting together a report of the data. I have aggregated and summed the data from many tables to get two tables that look like the following.

id | code | value          id | code | value
13 |  AA  | 0.5            13 |  AC  | 2.0
13 |  AB  | 1.0            14 |  AB  | 1.5
14 |  AA  | 2.0            13 |  AA  | 0.5
15 |  AB  | 0.5            15 |  AB  | 3.0
15 |  AD  | 1.5            15 |  AA  | 1.0

I need to get a list of id's, with the code (sumed from both tables) with the largest value.

13 |  AC
14 |  AA
15 |  AB

There are 4-6 thousand records and it is not possible to change the original tables. I'm not too worried about performance as I only need to run it a few times a year.

edit: Let me see if I can explain a bit more clearly, imagine the id is the customer id, the code is who they ordered from and the value is how much they spent there.

I need a list of the all the customer id's and the store that customer spent the most money at (and if they spent the same at two different stores, put a value such as 'ZZ' in for the store name).