This has worked for me:
you need to identify the attribute ids for all global attributes then delete all the values from the catalog_product_entity_*
tables that have the attribute id one of those identified above and the store id field not zero.
DELETE FROM `catalog_product_entity_int`
WHERE
store_id <> 0 AND
attribute_id IN (
SELECT attribute_id
FROM catalog_eav_attribute
WHERE is_global = 1
)
Do the same for the tables catalog_product_entity_varchar
, catalog_product_entity_text
, catalog_product_entity_datetime
, catalog_product_entity_decimal
.
Rebuild your indexes when your are done.
Note: The select from catalog_eav_attribute
in the way I wrote it will give you attribute ids for the global category attributes also, but that's not important since in the product tables you don't have category attributes references.
Also, before trying this, backup your database in case I missed something.
Source: https://magento.stackexchange.com/a/42763/6501
Thanks to: https://magento.stackexchange.com/users/146/marius