title: Second normal form question
body: <p>I'm insecure about the way i'm thinking when I'm normalising. I'm designing a database for an fictional online pizza shop.</p>
  
  <p>consider a table with a concatenated key being order_nr and pizza_article_nr. </p>
  
  <p>I'm stuck with the pizza toppings. I'm thinking that taken litterally, they don't rely on the pizza since they technically speaking can exist on their own. Yet in reality they're always connected to a pizza. So then do they exist on their own so that I will deal with them in 3NF or does the column 'toppings' fail 2NF because it does rely on the pizza in practical reality?</p>