title: Dense_rank in sql
body: <p>I have the following table 'CarN' in sql server</p>
  
  <pre><code>    carID      ownerID      Make      Model         Year        Color
      C11         O11         Honda       A           2010        Red       
      C12         blue        Honda       B           2012        Blue      
      C13         O12         Maru        B           2014        Yellow    
      C12         blue        Honda       B           2012        Blue 
  </code></pre>
  
  <p>when I execute the query </p>
  
  <pre><code>select  *,dense_Rank() over(partition by model order by carid)
  from carN
  
  carID      ownerID      Make      Model         Year        Color     Rank
  C11         O11         Honda       A           2010        Red         1
  C12         blue        Honda       B           2012        Blue        1
  C12         blue        Honda       B           2012        Blue        1
  C13         O12         Maru        B           2014        Yellow      2
  </code></pre>
  
  <p>In result how it happened to get the same number '1' for the first three records ?</p>