title: SQL Server convert columns to rows
body: <p>I have a sql table with current value and previous value.</p>
  
  <pre><code>Id  Value1  PValue1 Value2  PValue2
  1   A       A       V       V1
  2   B       B1      W       W1
  3   C       C1      X       X
  </code></pre>
  
  <p>I want to compare them and display in a the following table if the value has changes.</p>
  
  <pre><code>Id  Column  Value   Pvalue
  1   Value2  V       V1
  2   Value1  B       B1
  2   Value2  W       W1
  3   Value1  C       C1
  </code></pre>
  
  <p>Is it possible in SQL 2008 without looping each column?</p>