title: Database - Superkeys
body: <p>I am currently trying to study about databases and came across the concept of superkeys, which confuse me a little bit, could someone help define what a superkey actually is? As far as my understanding goes a superkey is the column in a table which makes the tuple unique, is that right?</p>
  
  <p>Lets say I have three tables, CUSTOMER, ACCOUNT and TRANSACTION
  And they each looked something like the tables below:</p>
  
  <p><img src="https://i.stack.imgur.com/xXwHA.png" alt="enter image description here"></p>
  
  <p>Would 'cid' be the superkey for CUSTOMER? or are there more than one?
  Which superkey violates the tables? As far as I understand {num, type, desc} violates ACCOUNT as there is no distinct column in the table, is that correct?
  How about TRANSACTION? </p>
  
  <p>kindest regards,</p>
  
  <p>KRS</p>