SQL & PL/SQL

I have the following table:

columns: a, b;
values: 'val1', 'dfs, da, w4';
'val2', 'fbd, hsd, s, hgdf';

How can I write a query so that I return the following values?

values:
'val1', 'dfs';
'val1', 'da';
'val1','w4';
'val2', 'fbd';
'val2', 'hsd';
'val2', 's';
'val2', 'hgdf';