Updating only a few fields

I want to only update my stock only using csv importer however, when I upload a file with only sku, post_title and stock, it seems to delete other parts of the item, i.e. post content.

I do not want it to delete anything, only update stock figures.

Can anyone tell me what I am doing wrong.

Thanks

http://ww.wp.xz.cn/plugins/woocommerce-csvimport/