Magento按目录号加载

hi guys how can i get catalog number instead of default sku number?

$product = Mage::getModel('catalog/product')->loadByAttribute('sku',$str);

the above code fetch item by sku number, but how can i fetch item based on catalog number?

Thanks

Looks like you searched a lot by yourself before asking here ...

Does your catalog number refers to the entity_id ?

If so simply : $product = Mage::getModel('catalog/product')->load($entityId);