MYSQL SELECT max(ID) WHERE Onderdeel_ID=$Onderdeel_ID

Question

$result = mysql_query("SELECT max(Cardex_ID) FROM cardex WHERE Onderdeel_ID=$Onderdeel_ID"); if (!$result) { die('Could not query:' . mysql_error()); }

    $Cardex_ID = mysql_result($result, 0, 'Cardex_ID');

    echo $Cardex_ID;

    mysql_query("UPDATE cardex SET PADate=$PAdate, PAhours=$PAhours, PAcycles=$PAcycles, PAlanding=$PAlanding WHERE Cardex_ID=$Cardex_ID");

Answer 1

我建议您使用 PDO连接到您的数据库而不是使用通用连接。此外，如果 $Onderdeel_ID 是一个数字，则您不需要 ""

   $db = new PDO ('mysql:host=localhost;dbname=DB_NAME','DB_USER','DB_PASS');
    $sql = 'SELECT max(Cardex_ID) FROM cardex WHERE Onderdeel_ID='. $Onderdeel_ID;
    $result = $db->query($sql)->fetch(PDO::FETCH_ASSOC);
    echo 'SELECT';
    if (!$result) {
      echo 'RESULT';
    }

注意:使用语句 prepare 来防止 SQL 注入(inject)也是有效且首选的:

    $db = new PDO ('mysql:host=localhost;dbname=DB_NAME','DB_USER','DB_PASS');
    $db->prepare ( 'SELECT max(Cardex_ID) FROM cardex WHERE Onderdeel_ID=:Onderdeel_ID');
    $result = $db->execute( array( ':Onderdeel_ID' => $Onderdeel_ID ) );

此外，如果您仍然遇到问题，请检查您的 $Onderdeel_ID 是否已通过。一个简单的 var_dump($Onderdeel_ID); 就可以了