You are right, the SQL call is not saved. But typically the most time is spend on rendering the view. Fragment caching is all about saving that time. Next step after that is HTTP caching. Please have a look into my book https://www.amazon.com/Learn-Rails-5-2-Accelerated-Development/dp/148423488X
And feel free to post an example with a question on stackoverflow.com and send me an email with a link to that. => firstname.lastname@example.org I’ll be happy to answer it.