> But it may be my mistake as I don't sure how to get the value which
> the ResultSet is likely containing now.
>
> I wrote
> if(rs.first()) someVariable = rs.getInt(1);

You should use ResultSet.next() instead of first(). The first() method
should be used for scrollable result sets, which you have to construct
explicitly. AFAIK, this is requirement from the JDBC specification.

Probably the error message could be better...

Roman