[sqlite] How to do NULL Handling in SELECT Statement?

[Stefan Finzel]

Hi,
what is the correct way to query for NULL-values? I use  SQLite version 
3.2.0

create table t1(a int, b char);
insert into t1 values(1, '2');
insert into t1 values(3,NULL);
insert into t1 values(NULL,'4');
select * from t1  where b=NULL;
-- this gives no result at all
select * from t1  where b='';
-- this also gives no result
select * from t1  where b<>'';
-- this gives the expected result (but i wanted the reverse data set)
1|2
|4
-- so i tried
select * from t1  where not b<>'';
-- and still i get not the result i was looking for.
TIA
Stefan