Question

我试图在搜索后显示数据库中找到的行数。

这是我的代码：

$city =  $_POST['city'];
 $bloodType = $_POST['donorType'];

     $q = $db->prepare("SELECT count(*) FROM  `users` AS numusers WHERE `city` = :city  AND `bloodType` = :bloodType");
     $q->bindValue(":city",$city,PDO::PARAM_INT);
     $q->bindValue(":bloodType",$bloodType);
     $q->execute();

    while($row = $q->fetch(PDO::FETCH_ASSOC)){
    echo "<p align='center'><h5> There is/are <span class='red-text'>".$row['numusers']."</span> available donor(s) found.
    You must be a <b><a href='register.php'>registered user</a></b> to view their details.</h5></p>";
      }

这是我做的最后一次尝试。我收到此错误消息 `注意：未定义的索引：numusers

如何解决这些提示？

Answer 1

只需创建count(*)

的别名即可

SELECT count(*) AS numusers..

这将是

$q = $db->prepare("SELECT count(*) AS  numusers FROM `users` WHERE `city` = :city  AND `bloodType` = :bloodType");

Answer 2

PDO中有一种特殊方法可以检索此类数据 - 查询返回的单个值PDOStatement::fetchColumn()。所以你根本不必麻烦别名。

此外，while循环在这里是多余的。

$city =  $_POST['city'];
$bloodType = $_POST['donorType'];

$q = $db->prepare("SELECT count(*) FROM  `users` WHERE `city` = :city  AND `bloodType` = :bloodType");
$q->bindValue(":city", $city, PDO::PARAM_INT);
$q->bindValue(":bloodType", $bloodType);
$q->execute();
$numusers = $q->fetchColumn();

echo "<p align='center'><h5> There is/are <span class='red-text'>$numusers</span> available donor(s) found.
You must be a <b><a href='register.php'>registered user</a></b> to view their details.</h5></p>";

PDO执行后获取行数

2 个答案: