title: Create many rows and a single column from many columns
body: <p>I am using SQL (in SAS). I have a dataset (table) that looks like this:</p>
  
  <pre> Y1  Y2  Y3
  100 200 300</pre>
  
  <p>What I would like to return is two columns that look like this:</p>
  
  <pre>Year  Value
  1     100
  2     200
  3     300</pre>
  
  <p>What would be the SQL query to acheive this?</p>