Recently I have written an article on how to include the custom field value to API response in case it is related to the same database table. In addition to the previous blog post, I would like to describe how to add external attributes to a collection, when the attribute values are stored in separate database tables.
Recently, we have faced with an issue that looked like a default Magento behavior. It turns out that Magento keeps the product attribute value even if the attribute was removed from the current attribute set. This brief article describes the issue’s details and a shell script on how to remove the old unnecessary attribute values from the database.