title: Deleting rows that have no referring rows
body: <p>Lets say I have a table with a fk constraint to the table pk.</p>
  
  <p>I want to delete all rows that has no relation to it.</p>
  
  <p>Is there a way to skip the rows that has a constraint violation and remove all others.</p>
  
  <p>Perhaps a loop with a transaction for each row..</p>