title: Counting the duplicate and setting the record in calculated column in SQL
body: <p>I have a table <code>Student_Information</code>, with columns and data like: </p>
  
  <pre><code>ID StudentName FatherName NIC  No_of_Childrens Date_of_Birth Date_of_Admission 
  1   Mark        John      85                      2010-04-01    2015-04-19  
  2   Akbar       Aslam     89                      2009-05-01    2015-04-19
  3   Percul      John      85                      2010-04-01    2015-04-19  
  4   Ali         Aslam     89                      2009-05-01    2015-04-19
  5   Diglor      John      85                      2010-04-01    2015-04-19  
  6   Sabi        Aslam     89                      2009-05-01    2015-04-19
  </code></pre>
  
  <p>I want to count the <code>NIC</code> column for duplicates and give numbers to <code>no of childs</code> column. Like this:</p>
  
  <pre><code>ID StudentName FatherName NIC No_of_Childrens Date_of_Birth Date_of_Admission 
  1   Mark        John    85        1              2010-04-01 2015-04-19  
  2   Akbar       Aslam   89        1              2009-05-01 2015-04-19
  3   Percul      John    85        2              2010-04-01 2015-04-19  
  4   Ali         Aslam   89        2              2009-05-01 2015-04-19
  5   Diglor      John    85        3              2010-04-01 2015-04-19  
  6   Sabi        Aslam   89        3              2009-05-01 2015-04-19
  </code></pre>