Active record and NULL value ?

[eluser]ariok[/eluser]
Hi all,
I found this problem working with active record:
What i have to do if i need to insert a NULL value in my DB ?

if i have array data with:
"fieldone"=>"this value",
"fieldtwo"=>null

the query generated with $this->db->insert($array)... is something like:

Code:

(fieldone,fieldtwo) values ("this value",[b]"null"[/b])

But i want a query like

Code:

(fieldone,fieldtwo) values ("this value",[b]null[/b])

with null and not "null"....

there's a pratical way to obtain the second query instead first?

Thank you all ..

Ariok