title: SQL-Update under a external condition
body: <p>Is it possible to limit the execution of an SQL CRUD-statement with a condition that is completely unrelated to the table it is working on?</p>
  <p>E.g. execute the UPDATE only if there is a special date.</p>
  <pre><code>UPDATE tabfoo SET name=&quot;santa&quot; where id=&quot;123&quot;   // only if day = 31.12.
  </code></pre>
  <p>I like to have this inside a single statement. I know how to do it inside a script.
  Me platform would be MySql or SqLite.</p>