How to create node programmatically only if the title does not exist?

i create a module to create nodes from external db. In the first column of the table there is company Id. That works, but now i will only create a node, if a node with the company id doesn´t exist.

  function example_create_nodes() {

  // Get Data from external DATABASE
  $result = db_query('SELECT * FROM wirdfit.wirdfit_data');

 // $node = (object) array();
 foreach ($result as $row) {
  $node = (object) array();
  $node->language = LANGUAGE_NONE;
  $node->type = 'page';
  $node->title = $row->id;
  node_object_prepare($node);  //Set some default values

 // Try to set your custom field

  $node->field_id($node->language)(0)('value') = $row->id;
  $node->field_post_title($node->language)(0)('value') = $row->post_title;
  $node->field_post_content($node->language)(0)('value') = $row->post_content;

  $path = 'content/mytest-' . date('YmdHis');
  $node->path = array('alias' => $path);
  $node = node_submit($node);
  $node->is_new = TRUE;

I think there should be an If statement, but don´t get it.
would be very grateful if anybody could help