title: Does Composite keys allows Duplicate
body: <p>I need to know whether Composite keys allows a duplicate values in it?</p>
  
  <p>For eg:</p>
  
  <p>I have 2 tables.</p>
  
  <p>1) Table 'Student' which has fields studentID(PK),standard,address.</p>
  
  <p>2) Table 'Class ' which has fields classID(PK),classname,studentID(FK).</p>
  
  <p>By having the composite key as (classID,studentID), Does it allows Duplicate Values??</p>
  
  <p>Exactly what I want to know is, is there any possibility to enter duplicate values in the classID field of Class Table? Because I cant enter duplicate values into classID as it is a primary key field.</p>
  
  <p>Will Composite key help me in achieving this? Kindly help me in this.</p>