Question

我目前正在为上传系统创建一个数据库 - 我使用一个选择框来限制添加到数据库的类别数。

<select name="category">
<?php
$conn = mysqli_connect("localhost", "blah", "blah") or die ("No connection");

mysqli_select_db($conn, "UPLOAD") or die("db will not open");

$query = "SELECT category FROM details GROUP BY category";

$result = mysqli_query($conn, $query) or die("Invalid query");

while($row = mysqli_fetch_array($result)) {
                echo "<option value=\"" . $row[0] . "\">" . $row[0] . "</option>";
                }               
             mysqli_close($conn);
            ?>
     </select>

    <select name="reaction">
            <?php
            $conn = mysqli_connect("localhost", "blah", "blah") or die ("No connection");

            mysqli_select_db($conn, "UPLOAD") or die("db will not open");

            $query = "SELECT reaction FROM details GROUP BY reaction";

            $result = mysqli_query($conn, $query) or die("Invalid query");

            while($row = mysqli_fetch_array($result)) {
                echo "<option value=\"" . $row[0] . "\">" . $row[0] . "</option>";
                }               
             mysqli_close($conn);
            ?>

虽然两个查询是相同的 - 只有类别（顶部查询）停止从我的数据库重复多个数据。当我查看我的数据库时 - 这就是我所发现的（我有预感可能是问题）。

INSERT INTO `details` (`name`, `category`, `reaction`, `photo`, `date_added`) VALUES
('Mase Laughing', 'Funny', 'Laugh\n', 'mase-laugh.gif', '2013-05-01 07:16:26'),
('Movie Wink', 'Cheeky', 'Wink\n', 'movie-wink.gif', '2013-05-02 12:33:12'),
('Tarzan Giggle', 'Funny', 'Wink\r\n', 'tarzan-laugh.gif', '2013-05-02 01:33:00');

除了我得到这些奇怪的\r\n字母的反应之外 - 有人有主意吗？提前谢谢。

Answer 1

这些是“回车”（\ r）和“换行符”（\ n）字符。这些命令告诉您的计算机走到行尾和新行。

要阻止您的网页显示重复的类别，请更改此选项：

$query = "SELECT category FROM details GROUP BY category";

进入这个：

$query = "SELECT distinct category FROM details GROUP BY category";

它不会阻止您的数据库存储重复的类别（您不需要，否则您只能保存每个类别的一（1）行详细信息，但它会阻止您的下拉列表（选择）显示因此，根据你展示的细节，它会给你一个带有'Funny'和'Cheecky'值的下拉菜单，两者都只显示一次。将“distinct”添加到您的其他SQL语句中也可以重复删除反应：

$query = "SELECT DISTINCT reaction FROM details GROUP BY reaction";

Answer 2

这里我通过减少冗余代码来更新原始问题

<?php
    $conn = mysqli_connect("localhost", "root", "") or die ("No connection");
    mysqli_select_db($conn, "test") or die("db will not open");
?>
<select name="category">
<?php

    $query = "SELECT category FROM details GROUP BY category";
    $result = mysqli_query($conn, $query) or die("Invalid query");
    while($row = mysqli_fetch_array($result)) {
        echo "<option value='" . $row[0] . "'>" . $row[0] . "</option>";
    }               
?>
</select>

<select name="reaction">
<?php
    $query = "SELECT reaction FROM details GROUP BY reaction";
    $result = mysqli_query($conn, $query) or die("Invalid query");

    while($row = mysqli_fetch_array($result)) {
        echo "<option value='" . $row[0] . "'>" . $row[0] . "</option>";
    }               
    mysqli_close($conn);
?>
</select>

MySQL选择框复制 - 复制一个字段选项但不复制另一个（查询相同）

2 个答案: