PHP + mysql_num_rows

Question

有沒有更有效的方法來進行以下操作？

$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 />';
    }
}

除了使用兩個查詢之外 ，沒有其他辦法了嗎？

Answer 1

您現在兩次檢索相同的東西，對嗎？ 如果根據查詢1存在一些數據，請通過查詢2再次檢索該數據並顯示它。 為什么不簡單地使用第二個查詢？

$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

您應該能夠像這樣重用查詢：

$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 />';
    }
}

Answer 3

從根本上說，它們是相同的查詢，不是嗎？

你為什么不能做：

$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

只需使用：

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

為什么要計數？

如果執行類似的操作，則只應計算可能的行數

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";
}