title: Convert datetime column to smallint
body: <p>I have a column called MyYear that is of type datetime. It only stores the year though, so I want to change it to smallint.</p>
  
  <p>When I try to run this:</p>
  
  <pre><code>ALTER TABLE MyTable
  ALTER COLUMN MyYear smallint
  </code></pre>
  
  <p>I get this error:</p>
  
  <blockquote>
    <p>Implicit conversion from data type datetime to smallint is not
    allowed. Use the CONVERT function to run this query.</p>
  </blockquote>
  
  <p>When I run this:</p>
  
  <pre><code>UPDATE MyTable
  set MyYear=YEAR(MyYear)
  </code></pre>
  
  <p>It does something funky and sets all the years to 1905.</p>
  
  <p>I am using SQL Server.</p>