[EDIT: see below] During a job interview, when they ask if you
   know something, quickly ask yourself, "Can I learn this on the
   job?" If you think you can, then say "Yes I do". * Since every
   job has a probational period (1st for 3 weeks to see if you're
   not homicidal, and about 3 months to see if you can hack it),
   it's enough time for you to learn whatever you said "yes" to. *
   EDIT: A straight "Yes, I do", if it is an absolute lie, be
   careful. Might be best avoided. What might be better is: "I
   don't know the specifics of what you need for this position, but
   I'm a fast learner and I'll pick up what I need to know quickly,
   as I have comparable knowledge in...[x], [y], [z], etc",
   highlighting transferable skills. I wrote this because I've seen
   too many people who continue to stock shelves (nothing wrong
   with stocking shelves mind you) because they're afraid to try
   something new. They may lack the schooling, but they have the
   knowledge. They may lack the certification, but they're capable
   of the job. But they're afraid because they don't feel official
   enough. They get stopped at the gates of Human Resources without
   realizing there's other ways to get employment that can make use
   of their skills.