PDO Echo 10值按降序排列

Question

I'm trying to echo out 10 numbers from my database in descending order sort of like a Highscores table.

This is my code

$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?>

I'm new to PDO/PHP I didn't get any errors it just doesn't print anything from my table its just blank ;/

Answer 1

you have to fetch the results in a array, and then echo the elements of the array.

$db = new PDO("mysql:host=$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.";
}

In queries that return large results I wouldn't use $stmt->fetchAll(). I would use fetch in a while loop like this:

$db = new PDO("mysql:host=$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.";
}

The difference between the first code chunk and the second is that in 1st chunk, we fetch all the results in a array and print them. In the second one tho, we print the data as we retrieve them one by one with PDOStatement::fetch()

Answer 2

You need to fetch the data from the object. I'll provide a link rather than code that will be helpful to you.

It should give you good introduction. It covers your question.

http://wiki.hashphp.org/PDO_Tutorial_for_MySQL_Developers#Running_Simple_Select_Statements