SQLite Forum

Shortcut to change a non changing update or upsert in a noop
Yes, I've noted this too, and as Mr. Hound reported, the whether any single row is updated or not is irrelevant, it's more to do with if any row on a specific page is changed that decides if it gets written to disk - that is, assuming we are correct in thinking that SQLite checks it so. The non changes may be brought about by a completely other mechanism.

Either way, I'm thinking more and more that SQLite writes only when needed and any query parts to try and "help" it is a waste of CPU cycles - but I am still not 100% sure.