In my case, I need to change the collation of all varchar columns in the database to UTF-8. I tried a modified version of
this answer on a test database and it worked great. "Finally," I thought, "I can put this collation nonsense behind me." Tried running it on a local copy of the real database. Hundreds of errors--because of indexes or something? But I don't see any indexes on those columns...? Argh!