php - mysql php在选择后处理没有数据

Question

我想知道执行查询后如何处理无数据或错误代码1329。

$stmt = $this->db->prepare('SELECT Username FROM Users WHERE device_id=?');
$stmt->bind_param("s", $device_id);
$flag = $stmt->execute();
$stmt->bind_result($Username);

我期望这段代码能够通过，但是自从它执行以来，该标志就是 true。

Answer 1

我建议这样做:

$stmt = $this->db->prepare('SELECT Username FROM Users WHERE device_id=?');
$stmt->bind_param("s", $device_id);
$stmt->execute();
$stmt->bind_result($Username);
if($stmt->fetch()) {
    echo "Found $Username";
} else {
    echo "Did not find any user";
}
$stmt->close();