php,mysql页面查询速度慢，如何优化查询？

如图：麻烦大神帮忙写写。优化逻辑我大概理解但是代码不会写。或者输出session，设置过期时间。或者输出数组，限定数据读取数量。或者合并二个查询到一个查询。等等。我理解这个意思但是不会写代码，求大神帮忙，散分！
代码贴上：
$result = mysql_query("select id from food");

$total = mysql_num_rows($result);//总记录数
$pageSize = 6; //每页显示数

$totalPage = ceil($total/$pageSize); //总页数
$startPage = $page*$pageSize;

$arr['total'] = $total;
$arr['pageSize'] = $pageSize;
$arr['totalPage'] = $totalPage;
$query = mysql_query("select id,title,pic from food order by id asc limit $startPage,$pageSize");
while($row=mysql_fetch_array($query)){
$arr['list'][] = array(
'id' => $row['id'],
'title' => $row['title'],
'pic' => $row['pic'],
);
}

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