Often, you'll want to add a column to a collection used in a grid, and to do so you'd use _prepareCollection():

protected function _prepareCollection()
{
    $collection = Mage::getResourceModel($this->_getCollectionClass());
  ...

This code shows all possible configuration options for an attribute that I know of, you need not include all of these when adding an attribute (although it won't hurt)

$installer = Mage::getResourceModel('catalog/setup', 'catalog_setup');

...

Using the database to inspect EAV-based entity types can be a real pain in the ass, so here are a bunch of queries that let you inspect some popular EAV entity types easily. This practice can be applied to any EAV entity type, however as there are...

To see a list of all attribute sets, groups, and associated attributes for products, use this SQL. BONUS! Also shows the sort ordering, useful for determining which sort_order you need to place an attribute in a certain position:

SELECT...

Declare an admin layout XML file for your module in your config.xml:

<config>
    <adminhtml>
        <layout>
            <updates>
                <your_module>
                    <file>your-module.xml</file>
    ...

We had a situation whereby a client placed an order and went through Sage Pay
succesfully, however the order was not able to be created on Magento, so we had
an error stating "WARNING - There are approved Sage Pay transactions that have
no associa...

In summary - making a credit memo can increase the stock quantity but will never set the "Stock Availability" of the product to "In Stock", whereas a config option can control whether an order cancellation sets "In Stock" automatically. Denying a ...

Magento has a Datetime backend model but formats a Zend_Date object without the time. So if you want to store datetime (actually with time) you will need to setup your own backend model.

Here is how i've done it:

class Namespace_Module_Mod...

Overview

A overview for those familiar with making flat models:

• Your config is standard, your table name takes the form of the base (entity) table
• You name your resource models as normal (so by class name, you can't tell the difference b...

Both use the same block, as we can see in page.xml:

<block type="core/messages" name="global_messages" as="global_messages"/>
<block type="core/messages" name="messages" as="messages"/>

When you add a message, you add it to the session...