Group data by distinct names with their values sum

Question

I have data in google-sheets in the next format (multiple paired columns):

Source: | Value: | Source: | Value: | ...
Name1     100    |  Name1     20
Name2     50     |  Name2     60
Name1    -10     |  Name3     600
Name3    -150    |  Name2     -700
Name1     500    |  Name2     50
...

How can I group it by name and sum values? I need to achieve this:

uniq(Source): | sum(Value):
Name1           1000
Name2           1400
Name3           -100
...

Answer 1

=QUERY({A2:B; C2:D}, 
 "select Col1,sum(Col2) 
  where Col1 is not null 
  group by Col1 
  label sum(Col2)''")