What a crack ... I don't like when I can't understand .

-My version is 1.5.0
-I tried with 0 and 1 and no change
- I got mysql under query logging
-When I import ( in this case by updating the already imported product.. result don't change when product is new ) I can see the sql log:

UPDATE products SET
products_price = '135.9',products_image = 'xxxx/xxxxxxx.pg',
products_weight = '0',
products_discount_type = '0',
products_discount_type_from = '0',
product_is_call = '0',
products_sort_order = '0',
products_quantity_order_min = '0',
products_quantity_order_units = '0',
products_priced_by_attribute = '0',
product_is_always_free_shipping = '0',
products_tax_class_id = '1',
products_date_available = NULL,
products_date_added = '2015-01-24 00:00:00',
products_last_modified = CURRENT_TIMESTAMP,
products_quantity = '1',
manufacturers_id = '56',
products_status = '1',
metatags_title_status = '0',
metatags_products_name_status = '0',
metatags_model_status = '0',
metatags_price_status = '0',
metatags_title_tagline_status = '0' WHERE (products_id = '8917')

As we can see the column products_quantity_mixed is not present on update or insert ( I have also did a general search for this field in all module's files ) action. That's why is being imported with default 0 column value.

Am I doing something wrong here ?