title: Normalization UNF to 1NF
body: <p>When normalizing a relation with multi-value attributes, we decompose it as a new relation with the primary key field and the values from the multi-valued attribute.</p>
  
  <p>The problem I have is, what is the primary key for that newly created attribute? </p>
  
  <p>If we use the same old primary key as the new one, since we repeat the values there with the values from the multi-valued attribute, how can we have unique values for the primary key field here?</p>
  
  <p>I have a table with customer_names, their hobbies and so on. Some people have more than 1 hobby, so now it's a multi-valued attribute. Now even if I create a new relation only with customer_name &amp; one hobby at a time, how can I add details of the people say who have 3 hobbies?</p>