php - PDO Echo 10 值按降序排列

Question

我正在尝试按降序从数据库中回显 10 个数字，就像高分表一样。

这是我的代码

$conn = new PDO("mysql:host=HOST;dbname=NAME", "NAME", "PASSWORD");
$hs = $conn->query("SELECT exp FROM login ORDER BY number DESC LIMIT 10");


<? echo $hs?>

我是 PDO/PHP 新手，我没有收到任何错误，它只是没有从我的表中打印任何内容，它只是空白；/

Answer 1

您必须获取数组中的结果，然后回显数组的元素。

$db = new PDO("mysql:host=$db_hostname;dbname=$database", $db_username, $db_password);

$sql = "SELECT exp FROM login ORDER BY number DESC LIMIT 10";

if ($stmt = $db->query($sql)) //PDO::query() returns a PDOStatement on success or false on failure.
{
    //If we got a PDOStatement as a return value from PDO::Query() fetch the results and echo.

    if($numbers = $stmt->fetchAll(PDO::FETCH_ASSOC)) //This will fetch all results in associative array.
    {
        //If the array contained data, then echo them.
        foreach ($numbers as $num)
        {
            echo $num['exp'] . "<br />";
        }
    }
    else
    {
        //If the PDOStatement returned an empty array. Let us know.
        echo "No data in the array";
    }
}
else
{
    //If PDO::Query returned false, then something is wrong with our query. Or connection or whatever.
     echo "Query failed.";
}

在返回大量结果的查询中，我不会使用 $stmt->fetchAll()。 我会在 while 循环中使用 fetch，如下所示:

$db = new PDO("mysql:host=$db_hostname;dbname=$database", $db_username, $db_password);

$sql = "SELECT exp FROM login ORDER BY number DESC LIMIT 10";

if ($stmt = $db->query($sql)) //PDO::query() returns a PDOStatement on success or false on failure.
{
    //If we got a PDOStatement as a return value from PDO::Query() !!!ECHO WHILE FETCHING!!! 
    while($row = $stmt->fetch(PDO::FETCH_ASSOC)) //This loop will keep going for as many rows as the PDOStatement returns.
    {
        echo $row['exp'] . "<br />";
    }
}
else
{
    //If PDO::Query returned false, then something is wrong with our query. Or connection or whatever.
     echo "Query failed.";
}

第一个代码块和第二个代码块之间的区别在于，在第一个代码块中，我们获取数组中的所有结果并打印它们。在第二个例子中，我们在使用 PDOStatement::fetch() 逐一检索数据时打印数据