Warning: mysql_num_rows(): supplied argument is not a valid MySQL result resource in

<?php
$SearchType = $_POST["SearchPlace"];
$host= 'localhost';
$user= 'user';
$passwd= 'password';
$database= 'dbase';
$table1= 'BUS';
$table2= 'STUDENT';

$connect= mysql_connect($host, $user, $passwd);
mysql_select_db($database);
$pquery = "select busNo from $table1 where place like '".$SearchType."'";

$squery = "select * from $table2 where busNo like '".$pquery."'"; 

$run = mysql_query($squery);
$num_results = mysql_num_rows($run);




if (!$SearchType )
{
echo "<b>You have not selected search details. Please go back and try again.</b>";
}
else
{

if (!$connect)
{
echo"</b>Error: Could not connect to database. Please try again later.</b>";
}

else
{
for ($i=0; $i<$num_results; $i++)
{ 
$row = mysql_fetch_array($run);

$IDNo= stripslashes($row["IDNo"]);
$sName= stripslashes($row["sName"]);
$startDate= stripslashes($row["startDate"]);
$endDate = stripslashes($row["endDate"]);
$sPhone= stripslashes($row["sPhone"]);
$OBox= stripslashes($row["OBox"]);
$busNo= stripslashes($row["busNo"]);

echo "<tr>\n";
echo "<td align=left>\n";
echo "<p> Student ID: ".$IDNo."";
echo "<br>Student Name: ".$sName."";
echo "<br>Starting Date: ".$startDate."";
echo "<br>Ending Date: ".$endDate."";
echo "<br>Student Phone: ".$sPhone."";
echo "<br>P.O.Box: ".$OBox."";
echo "<br>Bus number: ".$busNo."";
echo "</p>";
echo "</td></tr>\n";

echo "\n";
echo "\n";
echo "</table>\n";
}

}
}
?>

Hi I am getting this warning and I don't know why?!! :sad: :!:

please can you help me to find the error