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you can use collection to load all the product having attribute with null value

$collection = Mage::getModel('catalog/product')
->getCollection()
->addFieldToFilter(array>addAttributeToSelect('*')
   ->addFieldToFilter('weight', array('attribute'=>'weight','eq'=>''),
   ->addFieldToFilter('other_attribute_code', array('attribute'=>'other_attribute_code','eq'=>''), //Repeat this for more attributes
));

foreach($collection as $product){
    //Do something
    $product->getId();
}

you can use collection to load all the product having attribute with null value

$collection = Mage::getModel('catalog/product')
->getCollection()
->addFieldToFilter(array(
    array('attribute'=>'weight','eq'=>''),
    array('attribute'=>'other_attribute_code','eq'=>''), //Repeat this for more attributes
));

foreach($collection as $product){
    //Do something
    $product->getId();
}

you can use collection to load all the product having attribute with null value

$collection = Mage::getModel('catalog/product')
->getCollection()
->addAttributeToSelect('*')
->addFieldToFilter('weight', array('eq'=>''),
->addFieldToFilter('other_attribute_code', array('eq'=>''), //Repeat this for more attributes

foreach($collection as $product){
    //Do something
    $product->getId();
}
1
source | link

you can use collection to load all the product having attribute with null value

$collection = Mage::getModel('catalog/product')
->getCollection()
->addFieldToFilter(array(
    array('attribute'=>'weight','eq'=>''),
    array('attribute'=>'other_attribute_code','eq'=>''), //Repeat this for more attributes
));

foreach($collection as $product){
    //Do something
    $product->getId();
}