มันขึ้นอย่างนี้ Warning: mysql_num_rows() expects parameter 1 to be resource, boolean given in

<?php
session_start();

require 'connect.php';
 
$action = isset($_GET['a']) ? $_GET['a'] : "";
$itemCount = isset($_SESSION['cart']) ? count($_SESSION['cart']) : 0;
if (isset($_SESSION['qty']))
{
    $meQty = 0;
    foreach ($_SESSION['qty'] as $meItem)
    {
        $meQty = $meQty + $meItem;
    }
} else
{
    $meQty = 0;
}
if (isset($_SESSION['cart']) and $itemCount > 0)
{
    $itemIds = "";
    foreach ($_SESSION['cart'] as $itemId)
    {
        $itemIds = $itemIds . $itemId . ",";
    }
    $inputItems = rtrim($itemIds, ",");
    $meSql = mysql_query('SELECT * FROM tb_product WHERE id in ({$inputItems})');
    $meCount = mysql_num_rows($meSql);
} else
{
    $meCount = 0;
}
?>

<?php

$cfHost = "localhost";
$cfUser = "root";
$cfPassword = "2598083";
$cfDatabase = "mydatabase1";

$meConnect = mysql_connect($cfHost, $cfUser, $cfPassword) or die("Error conncetion mysql...");
$meDatabase = mysql_select_db($cfDatabase);
mysql_query("SET NAMES UTF8");
?>