Because each answer tries to select from a table with a particular name in an completely unspecified database. That table probably doesn't exist in most databases (it doesn't exist in any DB on any server I ever controlled - and I'll leave you to guess whether that means that I never controlled an HR or Payroll DB or that the table just happened to be named "seirbhiseach" or "Angestellte" instead of "employee".

In the real world it's no good doing what the commenter to whom I was replying suggested - just pick any database you have and then pick any table you have in that DB and then make the query refer to that table - whoever produced the requirement had something in mind, and surely it wasn't to let the developer pick the database and table at random. OK, so here we are talking about QOD instead of about real requirements, and the standard of questions is sometimes pretty low so adjusting the question might often make sense - but as a general rule I think we should try to treat the questions as if they are hard and fast, not subject to adjustment without obtaining agreement from the poser, because in the real world all the badly formulated (and often completely wrong-headed) requirements we see have to go through that negotiate with the poser process.