Mass Update of file_url

With enforced security in latest browsers, my old SDM links produce a security warning when trying to download. The download URL’s are “https://”. I wish to do a mass change, via SQL Query, to update ‘file_url’ to “https://”.

I have done the query via phpMyAdmin, successfully replacing “https://” with “https://”. But when checking the download via “Edit Downloads”, the “Downloadable File” field doesn’t show the change. Consequently the link continues to report -insecure-.

If I make the change manually in “Edit Download”, then the link is judged to be secure. But … I have nearly 2,000 download items. I really need to do it with a mass change. How might I do that?

Thanks for your ideas.