Question

我不明白这一点。我想从数据库中获取一个字符串，并将其添加到另一个字符串中以获取结果。

if (isset($_POST['key'])) {
    $conn = new mysqli('localhost', 'root', '', 'ams');
    if ($_POST['key'] == 'getStudentsData') {
        $start = $conn->real_escape_string($_POST['start']);
        $limit = $conn->real_escape_string($_POST['limit']);
        $set = $conn->query("SELECT * from teachers where id =$uid");
        $dat = $set->fetch_array();

        $dat = join(', ', $dat);
        $sql = $conn->query("SELECT * FROM logins WHERE subject IN $dat LIMIT $start, $limit");
        if (!empty($sql) && $sql->num_rows > 0) {
            $response = "";
            while ( $data = $sql->fetch_array(MYSQLI_ASSOC)) {
                $response .= '
                        <tr class="text-center">
                            <td>' . $data["fname"] . '&nbsp' . $data["lname"] . '</td>
                            <td>' . $data["matno"] . '</td>
                            <td>' . $data["email"] . '</td>
                            <td>' . $data["phone_no"] . '</td>
                            <td class="text-center">
                                <button value="Edit" class="btn btn-primary"> ' . $user->i('upload') . '</button>
                                <button value="View" class="btn">' . $user->i('eye') . '</button>
                                <button value="Delete" class="btn btn-danger">' . $user->i('trash') . '</button>
                            </td>
                        </tr>
                    ';
            }
            exit($response);
        } else
            exit('reachedMax');
    }
}

错误是这样的：

注意：尝试获取财产＆＃39; num_rows＆＃39;第35行中的非对象

Answer 1

您需要为IN支撑括号！这将纠正您的sql语句。仍然我建议您在传递给sql查询之前是否为$dat添加检查。

$conn->query("SELECT * FROM logins WHERE subject IN ($dat) LIMIT $start, $limit");

那么最佳做法是明确检查查询结果是对还是错

 if ($sql === false) {
     exit('reachedMax');
 }
 //come here if the query is successfully executed

Answer 2

我以前有同样的问题。

 $q1 =  "SELECT * ".
            "FROM admin, student ".
            "WHERE admin.pcode = student.code AND admin.puser_name = student.puser_name AND admin.id IN (SELECT admin.id FROM admin ORDER BY admin.id DESC LIMIT 1) ";

该问题归因于LIMIT。我不知道为什么在我将LIMIT放在那边时会说错误，而当我从查询中删除Limit时错误消失了

注意：试图获得财产＆＃39; num_rows＆＃39;第35行

2 个答案: