How to use QueryFilter class to keep empty value data

Hi. 

I had 2 tables, after outer join the result looks like:

ID         name         status(enum)

=====================

1         name1        active        

2         name2       not_active

3         name3       (no data)

The reason value of status is empty for ID 3 is because there is no ID 3 record in the second table.

 Now I would like to filter out not active data, so I use following code:

QueryFilter    filter;

filter = query.addQueryFilter(datasource, fieldStr(datasourceName2, status));
filter.value (SysQuery::valueNot(enum2str(status::not_active)));

The result is :

===============

1         name1        active      

but I want to keep the record ID 3 like this:

================

1         name1        active      

3         name3       (no data)

how can I change the code?

thanks

Quatrani