Query Logic for aggregating data

I have the following data:

variable1 variable2 varialble3

1 .               0

2 .               1

3 .               0

4                 0

5 .               1

I would like to sum variable1 based on the value of variable2. All the variable1 items with a 0 in var2 should be summed including with the var1 that has a var2 of 1. The result is stored in var 3. So the final table should look like: 

variable1 variable2 variable3

1 .               0               0

2 .               1               3

3 .               0                0

4                 0              0

5 .               1             12

What kind of log query command could I use to do this? Thanks!