title: How to concatenate all strings from a certain column for each group
body: <p>Suppose I have this table [Table1]</p>
  
  <pre><code>Name    Mark
  ------- ------
  ABC     10
  DEF     10
  GHI     10
  JKL     20
  MNO     20
  PQR     30
  </code></pre>
  
  <p>What should be my SQL statement to retrieve a record that looks like this:
  (group by [mark]).
  I have done the 1 and 2 columns but don't know how to accomplish the third column (concat the [name] with the same [mark])</p>
  
  <pre><code>mark count     names
  ---- -----     -----------
  10       3     ABC,DEF,GHI
  20       2     JKL,MNO
  30       1     PQR
  </code></pre>
  
  <p>I'm using Microsoft SQL.
  Please help. Thanks</p>