title: mySQL on delete cascade conditions
body: <p>Can I add a conditions to a cascade definition to restrict deletion of rows, e.g. something like </p>
  
  <pre><code>...
  FOREIGN KEY (building_no)
    REFERENCES buildings (building_no)
    *WHERE `otherField` = '&lt;some value&gt;'*
  </code></pre>
  
  <p>I want to restrict deleting to only those records that have a certain value in another field? The condition is in the target table, i.e. the one where records are supposed to be deleted. </p>