get data from query and use it in the next query

[eluser]mvn1990[/eluser]
hi, I've got an issue with my query's. first i wanne get id's and to do that i use this query:

$email = $this->session->userdata('email');

$data['id_project'] = $this->db->select('id_project')
->from('tbl_invited')
->join('tbl_user', 'tbl_user.email = tbl_invited.email')
->where('email', $email);

then i wanne use the id's (some times more than one) to get data by using an other query for example:

$data['id_project'] = $this->db->select('name')
->from('tbl_project')
->where('id_project', 'the id's I got from my first query' );

thanks in advance