where with NULL values are not selected

I try to join two tables whereas some column values do have NULL values with
the following query:

select table1.column from table1, table2 where table1.column=table2.column

table1.column and table2.column may have NULL values. The problem is that
these columns where not selected. Does there exists any solution to
select/join the NULL value colums also.

I would be appeciate about any hint.

PostgreSQL 7.4.5

With best regards
Horst Duester

---------------------------------
 
Dr. Horst Düster
GIS-Koordinator /Amtschef Stv.

Kanton Solothurn 
Amt für Geoinformation
Abteilung SO!GIS Koordination
Werkhofstr. 65
CH-4509 Solothurn

Tel.: ++41 (0)32 627 25 32
Fax: ++41 (0)32 627 22 14

horst(dot)duester(at)bd(dot)so(dot)ch
www.sogis.so.ch