php + mysql_num_rows

Question

is there a more efficient way of doing the following?

$total_a = mysql_query("SELECT `id` FROM `table` WHERE `this` = 'that'");
$total_b = mysql_num_rows($total_a);

if(!$total_b)
{
    echo 'no results';
}
else
{
    $a = mysql_query("SELECT `id`, `time` FROM `table` WHERE `this` = 'that' ORDER BY `time` DESC");
    while($b = mysql_fetch_assoc($a))
    {
        echo $b['id'].'-'.$b['time'].'<br />';
    }
}

there is no other way around than using two queries for this, is there?

Answer 1

You're retrieve the same thing twice now, right? If some data exists according to query 1, retrieve that data again with query 2 and display it. Why not simply use the second query?

$sql = "SELECT id, time FROM table WHERE this = 'that' ORDER BY time DESC";
$res = mysql_query($sql);
if (mysql_num_rows($res)) {
  while ($b = ...) {
    ...
  }
} else {
  echo 'no results';
}

Answer 2

just use:

$a = mysql_query("SELECT `id`, `time` FROM `table` WHERE `this` = 'that' ORDER BY `time` DESC");
while($b = mysql_fetch_assoc($a))
{
    echo $b['id'].'-'.$b['time'].'<br />';
}

why counting?

you only should count the possible rows if you do something like

if($count){
echo "starting the stuff";
$a = mysql_query("SELECT `id`, `time` FROM `table` WHERE `this` = 'that' ORDER BY `time` DESC");
while($b = mysql_fetch_assoc($a))
{
    echo $b['id'].'-'.$b['time'].'<br />';
}
echo "ending the stuff";
}

Answer 3

Fundamentally they are the same query are they not?!

Why can't you do:

$sql = "SELECT `id`, `time` FROM `table` WHERE `this` = 'that' ORDER BY `time` DESC";
$result = mysql_query($sql);

if(mysql_num_rows($result)){
    while($b = mysql_fetch_array($result))
    {
        echo $b['id'].'-'.$b['time'].'<br />';
    }
}
else{
  // no rows
}

Answer 4

You should be able to reuse the query like so:

$result = mysql_query("SELECT `id`, `time` FROM `table` WHERE `this` = 'that' ORDER BY `time` DESC");
$num_rows = mysql_num_rows($result);

if(!$num_rows)
{
    echo 'no results';
}
else
{
    while($row = mysql_fetch_assoc($result))
    {
        echo $row['id'].'-'.$row['time'].'<br />';
    }
}