我怎样才能在php / mysql中给出限制重复功能

Question

这是我的脚本，但我需要限制在mysql查询中我在LIMIT之前使用的mysql结果，但它没有用。

function display_menus($parent_id = 0){
 $i=0;
 $sql=mysql_query("SELECT * FROM customer_dog_details_db WHERE dog_id_parent = '$parent_id'  && username='root' && dog_id_filter='$_GET[dog_id]'");

if(mysql_num_rows($sql) > 0){

  echo "<ul class='tree'>";

    while ($row  = mysql_fetch_array($sql)){
      echo "<li><a href=''><span style='font-size:14px;'>". $row['dog_name'] ."</span>";
      echo "<br> ". $row['dog_id'] ." <br>";
      echo "". $row['sex'] ."<br>";
      echo "".$row['whelped_date']."<br>";
      echo "</a>";
      display_menus($row['dog_id']);
      echo "</li>";
    }

  echo "</ul>";
 }
}

display_menus();

Answer 1

use:
$sql=mysql_query("SELECT * FROM customer_dog_details_db WHERE dog_id_parent = '$parent_id' AND username='root' AND dog_id_filter='$_GET[dog_id]' limit 0,1");

instead of:

$sql=mysql_query("SELECT * FROM customer_dog_details_db WHERE dog_id_parent = '$parent_id' && username='root' && dog_id_filter='$_GET[dog_id]'");