I have over 1k products and would like to change the position in bulk.
Is there any fast & free way to change it? such as SQL?
I'd be nervous about doing this in SQL. I don't know a free way of doing it in bulk though. I have had success with import/extensions from this provider in the past though: http://www.commerceextensions.com/bulk-categories-import-export-csv-xml-magento-2.html
It's possible to do it with my software : Product Manager for Magento
You can copy and paste positions in the grid or drag and drop products to change positions.