How to split an array-column?

Hi,

I've got a table to import from csv that has an array-column like:

import ( id, array_col, ... )

Those arrays look like ( 42,  ";4941;4931;4932", ... )
They can have 0 or any number of elements separated by ;

So I'd need a result like this:
42, 4941
42, 4931
42, 4932

How would I get this?