如何在 PHP 中创建下拉查找字段？

Question

这里是 PHP 新手，

我在 MySQL Workbench 中有一个图书馆数据库，其中包含以下表：Student、Book 和 Checkin。我正在尝试使用 HTML 和 PHP 在网页上显示它，到目前为止它一直很好，直到尝试在签到表中将 s_id 显示为“s_name”，这是学生姓名，b_id 到 b_name 也是如此。我已经在 Workbench 中创建了外键连接，但无法弄清楚如何创建一个下拉选项来显示我已经在各自的表中创建的学生姓名和书名（而不是 s_id 和 b_id）。

在 MS Access 中查找字段非常简单，但事实证明，作为初学者，创建 PHP 版本很困难......这是现在的样子。

        <?php
                include('conn.php');
                $query=mysqli_query($conn,"select * from `checkin`");
                while($row=mysqli_fetch_array($query)){
                    ?>

                    <tr>
                        <td><?php echo $row['c_id']; ?></td>
                        <td><?php echo $row['s_id']; ?></td>
                        <td><?php echo $row['b_id']; ?></td>
                        <td><?php echo $row['c_date']; ?></td>
                        <td><?php echo $row['c_in']; ?></td>
                        <td>
                            <a href="edit_checkin.php?id=<?php echo $row['c_id']; ?>">Edit</a>
                            <a href="delete_checkin.php?id=<?php echo $row['c_id']; ?>">Delete</a>
                        </td>
                    </tr>
                    <?php
                }
            ?>
        </tbody>
    </table>
</div>

非常感谢任何帮助或提示！

Answer 1

在这里，现在有准备好的查询：

lib4.php

<form action='add_borrowing1.php' method='post'>
          <br>
          <select name="student">
        <?php
          $link = mysqli_connect("localhost", "root", "", "library");
          $sql = "SELECT DISTINCT studentId, studentName
          FROM students";
          $result = mysqli_query($link, $sql);
          print "<option value='students' selected>Students</option>";
          While ($row = mysqli_fetch_assoc($result))
            {
            print "<option value=" . $row["studentId"] . ">"
          . $row["studentName"] . "</option>";
            }
        ?>
          </select>
                    <p>Book:</p>
          <br>
          <select name="book">
        <?php
          $link = mysqli_connect("localhost", "root", "", "library");
          $sql = "SELECT DISTINCT bookId, bookName
          FROM books";
          $result = mysqli_query($link, $sql);
          print "<option value='books' selected>Books</option>";
          While ($row = mysqli_fetch_assoc($result))
            {
            print "<option value=" . $row["bookId"] . ">"
          . $row["bookName"] . "</option>";
            }
        ?>
          </select>
          <input type="submit" />
          </form>

          <?php
          if (!isset($_GET["raw"])) {
            echo "";
          }
          else {
            echo "Borrowing has been successfully added!";
          }

?>

add_borrowing.php
======================
<?php
$book = $_POST["book"];
$student = $_POST["student"];
$link = mysqli_connect("localhost", "root", "", "library");
        $sql = "INSERT INTO borrowing (bookId, studentId) VALUES (?,?)";


$stmt = mysqli_prepare($link, $sql);

            /*
            Explanation:
            i Integers
            d Doubles
            b Blobs
            s Everything Else 
            */
            mysqli_stmt_bind_param($stmt, "ii", $book,
                                   $student);
            mysqli_stmt_execute($stmt);
                mysqli_stmt_close($stmt);
                mysqli_close($link);

header("Location:lib4.php?raw=1");
?>