Есть таблицы


Они связанны между собою
и есть скрипт для вывода и удаления данных из этих таблиц, помогите написать запрос к удалению строк таким образом чтобы при удалении данных материнской таблицы удалилис и дочерные, Есть delete.php но он удаляет долько материнский, а дочерные не удаляются

delete.php

[PHP]<?php

$host="localhost"; // Host name
$username="root"; // Mysql username
$password=""; // Mysql password
$db_name="forum"; // Database name
$tbl_name="forum_question"; // Table name

// Connect to server and select databse.
mysql_connect("$host", "$username", "$password")or die("cannot connect");
mysql_select_db("$db_name")or die("cannot select DB");

// get value of id that sent from address bar
$id=$_GET['id'];

// Delete data in mysql from row that has this id
$sql="DELETE FROM $tbl_name WHERE id='$id '";
$result=mysql_query($sql);

// if successfully deleted
if($result){
echo "Deleted Successfully";
echo "<BR>";
echo "<a href='index.php'>Back to main page</a>";
}

else {
echo "ERROR";
}
?>

<?php
// close connection
mysql_close();
?>[/PHP]



index.php



[PHP]<?php

$host="localhost"; // Host name
$username="root"; // Mysql username
$password=""; // Mysql password
$db_name="forum"; // Database name
$tbl_name="forum_question"; // Table name

// Connect to server and select databse.
mysql_connect("$host", "$username", "$password")or die("cannot connect");
mysql_select_db("$db_name")or die("cannot select DB");

$sql="SELECT * FROM $tbl_name ORDER BY id DESC";
// OREDER BY id DESC is order result by descending

$result=mysql_query($sql);
?>

<table width="90%" border="0" align="center" cellpadding="3" cellspacing="1" bgcolor="#CCCCCC">
<tr>
<td width="6%" align="center" bgcolor="#E6E6E6"><strong>#</strong></td>
<td width="53%" align="center" bgcolor="#E6E6E6"><strong>Topic</strong></td>
<td width="15%" align="center" bgcolor="#E6E6E6"><strong>Views</strong></td>
<td width="13%" align="center" bgcolor="#E6E6E6"><strong>Replies</strong></td>
<td width="13%" align="center" bgcolor="#E6E6E6"><strong>Date/Time</strong></td>
</tr>

<?php



// Start looping table row
while($rows=mysql_fetch_array($result)){
?>
<tr>
<td bgcolor="#FFFFFF"><? echo $rows['id']; ?></td>
<td bgcolor="#FFFFFF"><a href="view_topic.php?id=<? echo $rows['id']; ?>"><? echo $rows['topic']; ?></a><BR></td>
<td align="center" bgcolor="#FFFFFF"><? echo $rows['view']; ?></td>
<td align="center" bgcolor="#FFFFFF"><? echo $rows['reply']; ?></td>
<td align="center" bgcolor="#FFFFFF"><? echo $rows['datetime']; ?></td>
<td align="center" bgcolor="#FFFFFF"><a href="delete.php?id=<? echo $rows['id']; ?>">delete</a></td>
</tr>

<?php
// Exit looping and close connection
}
mysql_close();
?>

<tr>
<td colspan="5" align="right" bgcolor="#E6E6E6"><a href="create_topic.php"><strong>Create New Topic</strong> </a></td>
</tr>
</table>[/PHP]

add_topic.php



[PHP]<?php

$host="localhost"; // Host name
$username="root"; // Mysql username
$password=""; // Mysql password
$db_name="forum"; // Database name
$tbl_name="forum_question"; // Table name

// Connect to server and select database.
mysql_connect("$host", "$username", "$password")or die("cannot connect");
mysql_select_db("$db_name")or die("cannot select DB");

// get data that sent from form
$topic=$_POST['topic'];
$detail=$_POST['detail'];
$name=$_POST['name'];
$email=$_POST['email'];

$datetime=date("d/m/y h:i:s"); //create date time

$sql="INSERT INTO $tbl_name(topic, detail, name, email, datetime)VALUES('$topic', '$detail', '$name', '$email', '$datetime')";
$result=mysql_query($sql);

if($result){
echo "Successful<BR>";
echo "<a href=index.php>View your topic</a>";
}
else {
echo "ERROR";
}
mysql_close();
?>[/PHP]
add_answer.php
[PHP]<?php

$host="localhost"; // Host name
$username="root"; // Mysql username
$password=""; // Mysql password
$db_name="forum"; // Database name
$tbl_name="forum_answer"; // Table name

// Connect to server and select databse.
mysql_connect("$host", "$username", "$password")or die("cannot connect");
mysql_select_db("$db_name")or die("cannot select DB");

// Get value of id that sent from hidden field
$id=$_POST['id'];

// Find highest answer number.
$sql="SELECT MAX(a_id) AS Maxa_id FROM $tbl_name WHERE question_id='$id'";
$result=mysql_query($sql);
$rows=mysql_fetch_array($result);

// add + 1 to highest answer number and keep it in variable name "$Max_id". if there no answer yet set it = 1
if ($rows) {
$Max_id = $rows['Maxa_id']+1;
}
else {
$Max_id = 1;
}

// get values that sent from form
$a_name=$_POST['a_name'];
$a_email=$_POST['a_email'];
$a_answer=$_POST['a_answer'];

$datetime=date("d/m/y H:i:s"); // create date and time


// Insert answer
$sql2="INSERT INTO $tbl_name(question_id, a_id, a_name, a_email, a_answer, a_datetime)VALUES('$id', '$Max_id', '$a_name', '$a_email', '$a_answer', '$datetime')";
$result2=mysql_query($sql2);

if($result2){
echo "Successful<BR>";
echo "<a href='view_topic.php?id=".$id."'>View your answer</a>";


// If added new answer, add value +1 in reply column
$tbl_name2="forum_question";
$sql3="UPDATE $tbl_name2 SET reply='$Max_id' WHERE id='$id'";
$result3=mysql_query($sql3);

}
else {
echo "ERROR";
}

// Close connection

mysql_close();
?>[/PHP]


За русский простите , я не русский!