select, where and null-values (or: select null<>'1' is fuzzy)

I've a problem when selecting values out a table.

manana=# select * from test;
 l1 | l2 | l3
----+----+----
 1  | 2  | 3
 2  | 3  | 4
 3  | 4  | 5
 4  | 5  | 6
    | 5  | 6
(5 rows)

where l1 is NULL in the last line.
now I do

manana=# select * from test where l1<>1;
 l1 | l2 | l3
----+----+----
 2  | 3  | 4
 3  | 4  | 5
 4  | 5  | 6
(3 rows)
and dont get the line with the null-entry !
In fact the problem is also describeable like this:

manana=# select NULL<>'1';
 ?column?
----------

(1 row)

This gives neither true nor false.

Why is this like this and how can I work around ?

thnx,
peter


--
mag. peter pilsl

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