sql server - SQL - If two records have same value in two columns, add third column -

i have table these values:

col1  | col2    | col3 |   1   | 2     |  3   |   4  | 5    |  6   |   4  | 7   |  8   |   4  | 7   |  9   |   

i want make query returns row every record in col1 , col2 both different in every other record, if both same in 2 records, result should 1 single row values in col1 , col2 , col3 sum in third column. result should be:

col1  | col2   | colnew |   1   | 2    |  3     |   4  | 5   |  6     |   4  | 7  | 17     |   

thank you.

use group by on columns want "group by" (1 , 2 in case). use sum on column want "sum" (3 in case).

select a.col1, a.col2, sum(a.col3) colnew test group a.col1, a.col2; 

sqlfiddle: http://sqlfiddle.com/#!3/070a3/4