CodeIgniter Active Records do not currently support sub-queries, However I use the following approach: $this->db->select('id');$this->db->from('table');$where_clause = $this->db->_compile_select(false,true);$this->db->_reset_select();#Create main query$this->db->select('*');$this->db->from('table1');$this->db->where("`id` NOT IN ($where_clause)", NULL, FALSE);return $this->db->get('',nul ... Continue