I have piece of PHP code written in Codeigniter framework that returns nothing (an empty set). Have a look at it and tell me what is wrong with it.
function sbsn($serial){
$this->db->select('asset_types.name as type_name,asset_brands.name as brand_name');
$this->db->from('asset_types,asset_brands,assets');
$this->db->where('assets.type_code','asset_types.code');
$this->db->where('assets.brand_code','asset_brands.code');
$this->db->where('serial_no',$serial);
$result = $this->db->get();
return $result;
}