title: Hard-Coding date string much faster than DateTime in SELECT?
body: <p>I have a very large table (15 million rows, this is an audit table).</p>
  
  <p>I need to run a query that checks for occurrences in the audit table that are after a certain date and meet certain criteria (I am looking for audit records that took place on current day only)</p>
  
  <p>When I run:</p>
  
  <pre><code>SELECT Field1, Field2 FROM AUDIT_TABLE WHERE AUDIT_DATE &gt;= '8/9/12'
  </code></pre>
  
  <p>The results come back fairly quick (a few seconds, not bad for 15M rows)</p>
  
  <p>When I run:</p>
  
  <pre><code>SELECT Field1, Field2 FROM AUDIT_TABLE WHERE AUDIT_DATE &gt;= @DateTime
  </code></pre>
  
  <p>It takes 11-15 seconds and does a full table scan.</p>
  
  <p>The actual field I am querying against is a DATETIME type, and the index is also on that field.</p>