title: mysql : delete rows where column = ID after delete ID
body: <p>I have 1 table like this </p>
  
  <pre><code>ID   parent
  1    null
  2    1
  3    1
  </code></pre>
  
  <p>now when I delete ID 1 I need auto delete all rows which parent = 1 . I try trigger a/b delete but give error for recursive trigger.</p>
  
  <p>thanks</p>