<?php
if(is_array($arrData)
{
 foreach($arrData as $data)
 {
  $objCount = "";
  $objCount = $this->Database->execute("SELECT count(id) AS counter FROM tl_table WHERE a=1 AND b=".$data[0]);
  //b is unique key criteria to identify dataset

  if($objCount->counter > 0)
   {
    //destroy dublettes
    $this->Database->execute("DELETE FROM tl_table WHERE a=1 AND b=".$data[0]);
   }
  //write to DB
  $this->Database->execute("INSERT INTO tl_table (a,b,c) VALUES (1,'".$data[0]."',3)");
 }
}
?>