Magento – DataFlow Export Duplicate SKUs in SKU Field

From this Magento KB article, it seems that we are limited to a set of predefined filters (name, sku, type, attribute_set, price/from, price/to, qty/from, qty/to, visibility, status)

To use another filter, you must create a small extension, example here: https://stackoverflow.com/a/7342066/729440

For categories, you'll want to load your category using Mage::getModel('catalog/category')->load($your_cat_id_here); and then use addCategoryFilter

So from what I can see the customer dataflow will not export system fields. If you look into the class app/code/core/Mage/Customer/Model/Convert/Parser/Customer.php you can see the function unparse. This converts the data into the csv rows.

At the very beginning of this method it loads all the system fields as defined in the xml app/code/core/Mage/Customer/etc/config.xml see node admin->fieldsets->customer_dataflow.

$systemFields = array();
foreach ($this->getFields() as $code=>$node) {
    if ($node->is('system')) {
        $systemFields[] = $code;
    }
}

Then during the parsing process the system will look through the customer data and process the data that it would like to export. The problem is that it will skip all data fields flagged as system.

if (in_array($field, $systemFields) || is_object($value)) {
    continue;
}

So you could do one of the following options:

1. Update the xml nodes so that updated_at is not a system field,
2. Update the unparse so that you can select some system fields to export,