Sum column based on criteria on another column

[Vemsom Helst]

Hello,
I want to sum the values in column A for distinct numbers in column B.
Example

1 100
2 50
4 50
1 20
1 80
4 40

Requested look:
1 100 200
2 50 50
4 50 90
1 20 200
1 80 200
4 40 90
Or:
1 200
2 50
4 90

I have tried with a few different queries:
- select distinct matnr, sum(KWMENG) from VBAP_0101 group by MATNR
- select KWMENG from( select distinct matnr, sum(KWMENG) from VBAP_0101 group by MATNR)

Preferably I want to have the first requested table and I thought I could do it easiest with a subquery but my query on't stick. Any ideas?

Thanks!