In magento there is a very good option in the admin to update all the attributes at the same time.
like if there are 100 products whose price has been changed and there are same price for all and you want to change them quickly and not by updating each single product , magento has a good option for you
In the admin go to
system -> manageproduct-> and there will be checkbox on the left in front of each product
Select the multiple products you want to update and than on the right top there is a option of action ,click on the dropdown and select update attribute and than press submit . You will see the atribute of products and than click on the CHANGEcheckbox of attribute which ever you want to update for selected products and than press save . The attribute for all the products will be updated
You can also select all if you want to update any attribute which has same value for all products .
