My QTableView has this structure:
Number, Month, Code.
Numbers are in first column, months in second, codes in third.

On example my tableview will looks so:
200, 02, 23
10, 02, 23
30, 03, 24

How can I do that function:
if values in second and third column values are the same, then make one line(is it correct term?) with that values, and in the first column program must to show the sum of all values of first columns.

So, the result must be:
210, 02, 23
30, 03, 24

How to do that? I really need help.