title: What does the "minimality" mean in database candidate keys?
body: <p>I was very confused by the idea given by my professor when studying about candidate key (but i feel sham to ask him :p )</p>
  
  <blockquote>
    <p>"no component of K can be eliminated without destroying 
        the uniqueness property         --- minimality"</p>
  </blockquote>
  
  <p>And i searched on wiki it says</p>
  
  <blockquote>
    <p>"there is no proper subset of these attributes for which (1) holds (which means that the set is minimal)." It also give an example but i don't understand.</p>
  </blockquote>
  
  <p>So my question is what does the "eliminated" here means? if it means remove the whole rows of data, then it should always keep the uniqueness of the data(because you can't lose uniqueness by removing a row of data). If it means only remove the single attribute of K and left a row with a empty "block", it looks silly and will destroy the data. So can someone give me some simple example for what does this property mean?(maybe one for the good one and one for the bad one) Thank you~</p>