LEFT JOIN 分页中断答案

【问题标题】：Pagination broken on LEFT JOINLEFT JOIN 分页中断
【发布时间】：2017-12-16 18:04:43
【问题描述】：

我已经更改了我的分页，因为它没有第一个/上一个和下一个/最后一个导航功能的版本。

我更改它的原因是因为页面底部会有 30 多个编号的链接，而且它很丑而且看起来不专业。

分页适用于我的所有页面，但网站上的两个部分除外。奇怪的是，这两个页面具有 LEFT JOIN，就像下面的示例一样，但不同之处在于它们依赖于为每个页面选择一个 categoryID 来显示数据。

以下是 PHP 和 MySQL 的新代码示例以及代码的 HTML。

工作 PHP 和 MySQL

//PAGINATION
try {
    $totalPages  = $DB->query(" SELECT COUNT(id) as rows 
                                FROM art_categories LEFT JOIN articles
                                ON articles.categoryID=art_categories.categoryID
                                WHERE articles.categoryID=art_categories.categoryID
                                AND art_categories.categoryID NOT IN
                                    (SELECT categoryID
                                     FROM art_categories
                                     WHERE categoryID=8)
                                AND articles.publishDate >= DATE_ADD( NOW( ) , INTERVAL -2 MONTH )
                                AND state = 1")
              ->fetch(PDO::FETCH_OBJ);

    $posts  = $totalPages->rows;
    $pages  = ceil($posts / $perpage);

    # default
    $get_pages = isset($_GET['page']) ? $_GET['page'] : 1;

    $data = array(

        'options' => array(
            'default'   => 1,
            'min_range' => 1,
            'max_range' => $pages
            )
    );

    $number = trim($get_pages);
    $number = filter_var($number, FILTER_VALIDATE_INT, $data);
    $range  = $perpage * ($number - 1);

    $prev = $number - 1;
    $next = $number + 1;

    $stmt = $DB->prepare("SELECT * FROM articles WHERE publishDate >= DATE_ADD( NOW( ) , INTERVAL -2 MONTH ) LIMIT :limit, :perpage");
    $stmt->bindParam(':perpage', $perpage, PDO::PARAM_INT);
    $stmt->bindParam(':limit', $range, PDO::PARAM_INT);
    $stmt->execute();

    $result = $stmt->fetchAll();

} catch(PDOException $e) {
    $error = $e->getMessage();
}

工作 HTML

<ul class="pagination">
    <?php

            if($result && count($result) > 0)
            { ?>
            <li <?php if($_GET['page'] >= 2) { echo('class=""'); } else { echo('class="disabled"'); } ?> >
                <a href="<?php if($_GET['page']==1 || $_GET['page']==0) { echo('#');} else { echo ('index.php?page=1'); } ?>">FIRST</a>
            </li>
            <li <?php if(!empty($_GET['page']) && $_GET['page']==1 || $_GET['page']==0) { echo('class="disabled"');} ?>>
                <a <?php if($_GET['page']==1 || $_GET['page']==0) { echo('class="disabled"');} ?> href="<?php if($_GET['page']==1 || $_GET['page']==0) { echo('#');} else { echo ('index.php?page='. $prev); } ?>">&laquo; PREVIOUS</a>
            </li>
            <li class="active">
                <a href="index.php?page=<?php echo $get_pages; ?>"><?php echo $get_pages; ?></a>
            </li>
            <li <?php if($_GET['page']==$pages) { echo('class="disabled"');} ?>>
                <a href="<?php if($_GET['page']==$pages) { echo('#');} else { echo ('index.php?page='. $next); } ?>">NEXT &raquo;</a>
            </li>
            <li <?php if($_GET['page']==$pages) { echo('class="disabled"');} ?>>
                <a href="<?php if($_GET['page']==$pages) { echo('#');} else { echo ('index.php?page='. $pages); } ?>">LAST</a>
            </li>

    <?php } ?>
</ul>

到目前为止，一切都很好。一旦我尝试在其他页面上为类别和广告商执行左 LEFT JOIN，我的分页就无法正常工作。

我收到以下错误代码：

注意：未定义的变量：导致第 15 行的 C:\wamp64\www\Bushvelder\categories.php

这是代码中的第 15 行：

if($result && count($result) > 0)

我将为类别页面添加下面的代码，因为我相信一旦我得到这个排序，我也将能够修复广告商页面的分页。

损坏的 PHP 和 MySQL

$catID = $_GET['categoryID'];

//PAGINATION
try {
    $totalPages  = $DB->query(" SELECT COUNT(id) as rows 
                                FROM art_categories LEFT JOIN articles
                                ON articles.categoryID=art_categories.categoryID
                                WHERE articles.categoryID={$catID}
                                AND articles.publishDate >= DATE_ADD( NOW( ) , INTERVAL -2 MONTH )
                                AND state = Publish")
              ->fetch(PDO::FETCH_OBJ);

    $posts  = $totalPages->rows;
    $pages  = ceil($posts / $perpage);

    # default
    $get_pages = isset($_GET['page']) ? $_GET['page'] : 1;

    $data = array(

        'options' => array(
            'default'   => 1,
            'min_range' => 1,
            'max_range' => $pages
            )
    );

    $number = trim($get_pages);
    $number = filter_var($number, FILTER_VALIDATE_INT, $data);
    $range  = $perpage * ($number - 1);

    $prev = $number - 1;
    $next = $number + 1;

    $stmt = $DB->prepare("  SELECT *
                            FROM art_categories LEFT JOIN articles
                            ON articles.categoryID=art_categories.categoryID
                            WHERE articles.categoryID={$catID}
                            AND articles.publishDate >= DATE_ADD( NOW( ) , INTERVAL -2 MONTH )
                            AND state = Publish
                            ORDER BY articles.publishDate DESC LIMIT :limit, :perpage");
    $stmt->bindParam(':perpage', $perpage, PDO::PARAM_INT);
    $stmt->bindParam(':limit', $range, PDO::PARAM_INT);
    $stmt->execute();

    $result = $stmt->fetchAll();

} catch(PDOException $e) {
    $error = $e->getMessage();
}

HTML 代码

<ul class="pagination">
    <?php

        if($result && count($result) > 0)
        { ?>
            <li <?php if($_GET['page'] >= 2) { echo('class=""'); } else { echo('class="disabled"'); } ?> >
                <a href="<?php if($_GET['page']==1 || $_GET['page']==0) { echo('#');} else { echo ('categories.php?categoryID='. $article['categoryID'] . '&amp;page=1'); } ?>">FIRST</a>
            </li>
            <li <?php if(!empty($_GET['page']) && $_GET['page']==1 || $_GET['page']==0) { echo('class="disabled"');} ?>>
                <a <?php if($_GET['page']==1 || $_GET['page']==0) { echo('class="disabled"');} ?> href="<?php if($_GET['page']==1 || $_GET['page']==0) { echo('#');} else { echo ('categories.php?'. $article['categoryID'] . '&amp;page='. $prev); } ?>">&laquo; PREVIOUS</a>
            </li>
            <li class="active">
                <a href="categories.php?categoryID=<?php echo $article['categoryID']; ?>&amp;page=<?php echo $get_pages; ?>"><?php echo $get_pages; ?></a>
            </li>
            <li <?php if($_GET['page']==$pages) { echo('class="disabled"');} ?>>
                <a href="<?php if($_GET['page']==$pages) { echo('#');} else { echo ('categories.php?'. $article['categoryID'] . '&amp;page='. $next); } ?>">NEXT &raquo;</a>
            </li>
            <li <?php if($_GET['page']==$pages) { echo('class="disabled"');} ?>>
                <a href="<?php if($_GET['page']==$pages) { echo('#');} else { echo ('categories.php?'. $article['categoryID'] . '&amp;page='. $pages); } ?>">LAST</a>
            </li>

    <?php } ?>
</ul>

我强烈怀疑我的 MySQL 搞砸了，但我不知道从哪里开始。任何帮助将不胜感激。

如果我在回答这个问题之前弄清楚了，我会发布我的发现。

编辑

好的，所以我用 LIMIT :limit, :perpage 修复了错误，但如上所述，我仍然在第 15 行收到错误。

【问题讨论】：

我怀疑你没有用 LIMIT 绑定任何东西。并通过 bindparam 传递变量
你需要传递参数，比如 LIMIT :perpage :limit

标签： php html mysql pagination

【解决方案1】：

这就是我为解决我的问题所做的。

第一我使用 var_dump($variable) 对与我的分页问题相关的所有变量进行了一些变量转储。

<?php echo var_dump($result); ?>
<?php echo var_dump($totalPages); ?>
<?php echo var_dump($pages); ?>
<?php echo var_dump($get_pages); ?>
<?php echo var_dump($posts); ?>
<?php echo var_dump($stmt); ?>
<?php echo var_dump($catID); ?>
<?php echo var_dump($article['categoryID']); ?>
<?php echo var_dump($_GET['page']); ?>

这让我了解了哪些变量有值，哪些是空值。

然后我转到我的原始代码：

$stmt = $DB->prepare("  SELECT *
                        FROM art_categories LEFT JOIN articles
                        ON articles.categoryID=art_categories.categoryID
                        WHERE articles.categoryID={$catID}
                        AND articles.publishDate >= DATE_ADD( NOW( ) , INTERVAL -2 MONTH )
                        AND state = Publish
                        ORDER BY articles.publishDate DESC LIMIT :limit, :perpage");
$stmt->bindParam(':perpage', $perpage, PDO::PARAM_INT);
$stmt->bindParam(':limit', $range, PDO::PARAM_INT);
$stmt->execute();

然后我通过 PHP 设置各种 SWITCH CASES 以查看当我单击菜单时 categoryID 是否确实发生了变化。这确实有效。

switch ($catID) {
        case 1:
            $stmt = $DB->prepare("  SELECT art_categories.*, articles.*
                                    FROM art_categories LEFT JOIN articles
                                    ON articles.categoryID=art_categories.categoryID
                                    WHERE articles.categoryID=1
                                    AND articles.publishDate >= DATE_ADD( NOW( ) , INTERVAL -2 MONTH )
                                    AND state = Publish
                                    ORDER BY articles.publishDate DESC LIMIT :limit, :perpage");
            break;
        case 2:
            $stmt = $DB->prepare("  SELECT *
                                    FROM art_categories LEFT JOIN articles
                                    ON articles.categoryID=art_categories.categoryID
                                    WHERE articles.categoryID=2
                                    AND articles.publishDate >= DATE_ADD( NOW( ) , INTERVAL -2 MONTH )
                                    AND state = Publish
                                    ORDER BY articles.publishDate DESC LIMIT :limit, :perpage");
            break;
        case 3:
            $stmt = $DB->prepare("  SELECT *
                                    FROM art_categories LEFT JOIN articles
                                    ON articles.categoryID=art_categories.categoryID
                                    WHERE articles.categoryID=3
                                    AND articles.publishDate >= DATE_ADD( NOW( ) , INTERVAL -2 MONTH )
                                    AND state = Publish
                                    ORDER BY articles.publishDate DESC LIMIT :limit, :perpage");
            break;
        case 4:
            $stmt = $DB->prepare("  SELECT *
                                    FROM art_categories LEFT JOIN articles
                                    ON articles.categoryID=art_categories.categoryID
                                    WHERE articles.categoryID=4
                                    AND articles.publishDate >= DATE_ADD( NOW( ) , INTERVAL -2 MONTH )
                                    AND state = Publish
                                    ORDER BY articles.publishDate DESC LIMIT :limit, :perpage");
            break;
        case 5:
            $stmt = $DB->prepare("  SELECT *
                                    FROM art_categories LEFT JOIN articles
                                    ON articles.categoryID=art_categories.categoryID
                                    WHERE articles.categoryID=5
                                    AND articles.publishDate >= DATE_ADD( NOW( ) , INTERVAL -2 MONTH )
                                    AND state = Publish
                                    ORDER BY articles.publishDate DESC LIMIT :limit, :perpage");
            break;
        case 6:
            $stmt = $DB->prepare("  SELECT *
                                    FROM art_categories LEFT JOIN articles
                                    ON articles.categoryID=art_categories.categoryID
                                    WHERE articles.categoryID=6
                                    AND articles.publishDate >= DATE_ADD( NOW( ) , INTERVAL -2 MONTH )
                                    AND state = Publish
                                    ORDER BY articles.publishDate DESC LIMIT :limit, :perpage");
            break;
        case 7:
            $stmt = $DB->prepare("  SELECT *
                                    FROM art_categories LEFT JOIN articles
                                    ON articles.categoryID=art_categories.categoryID
                                    WHERE articles.categoryID=7
                                    AND articles.publishDate >= DATE_ADD( NOW( ) , INTERVAL -2 MONTH )
                                    AND state = Publish
                                    ORDER BY articles.publishDate DESC LIMIT :limit, :perpage");
            break;
        case 8:
            $stmt = $DB->prepare("  SELECT *
                                    FROM art_categories LEFT JOIN articles
                                    ON articles.categoryID=art_categories.categoryID
                                    WHERE articles.categoryID=8
                                    AND articles.publishDate >= DATE_ADD( NOW( ) , INTERVAL -2 MONTH )
                                    AND state = Publish
                                    ORDER BY articles.publishDate DESC LIMIT :limit, :perpage");
            break;
    }

然后我查看了 VAR_DUMP 数据，并且 $result 变量仍然显示为空。所以我决定检查我的查询。我经历了多次查询代码迭代，尝试了不同的 JOIN 方法，看看它如何影响我的 VAR_DUMP 数据。

这表明我最初在 MySQL 查询中使用的 LEFT JOIN 没有问题，因为它与使用 LEFT JOIN 的其他页面一起工作.

我继续测试我的查询，直到最后成功！

$catID = $_GET['categoryID'];

//PAGINATION
try {

    $totalPages  = $DB->query(" SELECT COUNT(id) as rows 
                                FROM art_categories LEFT JOIN articles
                                ON articles.categoryID=art_categories.categoryID
                                WHERE articles.categoryID = {$catID}
                                AND articles.publishDate >= DATE_ADD( NOW( ) , INTERVAL -2 MONTH )")
              ->fetch(PDO::FETCH_OBJ);

    $posts  = $totalPages->rows;
    $pages  = ceil($posts / $perpage);

    # default
    $get_pages = isset($_GET['page']) ? $_GET['page'] : 1;

    $data = array(

        'options' => array(
            'default'   => 1,
            'min_range' => 1,
            'max_range' => $pages
            )
    );

    $number = trim($get_pages);
    $number = filter_var($number, FILTER_VALIDATE_INT, $data);
    $range  = $perpage * ($number - 1);

    $prev = $number - 1;
    $next = $number + 1;

    $stmt = $DB->prepare("  SELECT *
                            FROM art_categories LEFT JOIN articles
                            ON articles.categoryID=art_categories.categoryID
                            WHERE articles.categoryID = {$catID}
                            AND articles.publishDate >= DATE_ADD( NOW( ) , INTERVAL -2 MONTH )
                            ORDER BY articles.publishDate DESC LIMIT :limit, :perpage");
    $stmt->bindParam(':perpage', $perpage, PDO::PARAM_INT);
    $stmt->bindParam(':limit', $range, PDO::PARAM_INT);
    $stmt->execute();

    $result = $stmt->fetchAll();

} catch(PDOException $e) {
    $error = $e->getMessage();
}

所以在所有测试之后，似乎 AND state = Publish 是破坏我的分页并导致数小时的挫败感、浪费时间和抓挠的罪魁祸首。我创建的 ENUM 似乎有问题，用于检查内容是否保存为 DRAFT 或 PUBLISH 状态。

我从中学到了什么？

保持冷静，不要惊慌
使用 var_dump() 测试您的变量
设置不同的CASE SWITCHES对我很有帮助
正确解决您的问题
不要放弃
学到了一些新技巧

【讨论】：