gistfile1.txt

<?php


  $or = db_or();
  $or->condition('n.type', 'doctor');
  $or->condition('n.type', 'practice');

  $and = db_and();
  $and->condition('n.nid', '532', '<');

  $qry = db_select('node', 'n');

  $qry
    ->fields('n', array('nid'));
  $qry
    ->condition($or)
    ->condition($and);

  $res = $qry
    ->execute();
  
  foreach ($res as $row) {
    $nids[] = $row->nid;
  }


node_delete_multiple($nids);