I have a custom attribute for min_price I need to update this field using data from the cost field using a formula. (cost+1.50)/.84

Any ideas on how I can do this?

I've tried to make since of the EAV database and do it in MySQL directly but it's confusing to say the least.


  • do you need to do this in mysql or in magento itself? – David Manners Jul 5 '14 at 4:55
  • Doesn't matter, as long as I can do it without having to export/import all the time. – Brad Jul 5 '14 at 5:29
  • Use observer catalog_product_save_before And update the attribute – Charlie Jul 5 '14 at 7:26
  • @Charlie Do you suggest any demo code is that would show me how to do that? I can piecemeal it together from several sources, but I don't want to use bad info. Thanks – Brad Jul 5 '14 at 7:38

From reading your comments above, sounds like you want something that will update via the backend when you click save.

I have added 2 observers one for the normal backend category save and another for the mass update 'update attributes' on the category grid page.


<?xml version="1.0"?>




    <?php class Namespace_Module_Model_Observer
    protected $additionalValue = 1.50;
    protected $multiplicationValue = 0.84;

     * Handle catalog_product_save_before event
     * @param Varien_Event_Observer $observer
     * @return void
    public function catalogUpdateMinPrice(Varien_Event_Observer $observer)
        /** @var $product Mage_Catalog_Model_Product */
        $product = $observer->getEvent()->getDataObject();

        $cost = $product->getCost();
        $newMinPrice = null;

        if($cost != ""){
            $newMinPrice = ($cost+$this->additionalValue)/$this->multiplicationValue;



     * Handle catalog_product_attribute_update_before event
     * @param Varien_Event_Observer $observer
    public function catalogUpdateMinPriceMassaction(Varien_Event_Observer $observer)
        /** @var $block Mage_Adminhtml_Block_Catalog_Product_Edit_Action_Attribute_Tab_Attributes */
        $attributesData = $observer->getEvent()->getAttributesData();

        $cost = $attributesData['cost'];

        if($cost != ""){
            $newMinPrice = ($cost+$this->additionalValue)/$this->multiplicationValue;
            $attributesData['min_price'] = $newMinPrice;


  • I'm running the community version I noticed enterprise_pricepermissions in your answer, will this work with community? Thanks – Brad Jul 5 '14 at 18:42
  • Whoops, I have updated the answer now. Yes it will but use the updated version. (I just copied it from a enterprise observer and forgot to update that bit (it's just an identifier)) – James Anelay - TheExtensionLab Jul 5 '14 at 18:53
  • I think this code will work, if I knew a little more about magento. I've got a gist that shows my setup. Wondering if you could tell me where I went wrong. gist.github.com/btray77/0e34cda8fa751524b610 – Brad Jul 5 '14 at 20:34
  • Nearly :). Line 33 of your config.xml <Overnight_Pricer> should be </Overnight_Pricer>. (Personally I would also keep the following lines lowercase : 11,13,21,24,30,33 in your config.xml as is done in the core) – James Anelay - TheExtensionLab Jul 5 '14 at 20:41
  • did the changes, not creating log, and not updating pricing... – Brad Jul 5 '14 at 22:45

If it's a one time thing, you could consider doing it quickly via a spreadsheet (although I know others would strongly disagree). You could export the data pretty quickly via some sql

INNER JOIN catalog_product_entity_decimal ON catalog_product_entity_decimal.attribute_id = eav_attribute.attribute_id
INNER JOIN catalog_product_entity ON catalog_product_entity_decimal.entity_id = catalog_product_entity.entity_id
WHERE eav_attribute.frontend_label LIKE "%cost%"

This assumes -

  1. You only have the one store view
  2. The attribute you're referencing is "cost"
  3. The attribute you're referencing is a "price" attribute

So you can then export this as a csv, quickly process the calculation, and import it back it, either by an import tool like Magmi (recommended if you don't know what you're doing), or if you have a full grasp of this explanation, you could pop the results straight back in to the database (again, I know for many this is a cardinal sin).

However, always make a backup of your database before you try things like this. You really never can have too many backups.


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