I love to ask this very simple question in interviews: if a database index makes queries faster, why not add an index for every column on a table? I want them

I love to ask this very simple question in interviews: if a database index makes queries faster, why not add an index for every column on a table? I want them to say “the heck are you talking about, because that’s not how anything works?”… it does trip some people up though that just legitimately don’t understand what’s happening.