如何使第一级类别仅显示一次? [英] How do I get the first level category to display only once?

问题描述

我在mysql中设置了一个表，如下所示:

I have a table set up in mysql as follows:

我想创建一个侧边栏类别导航，其中包含父类别-子类别-以及可能存储在另一个表中的第三级类别.

I would like to create a sidebar category navigation with Parent category - subcategories - and possible third level categories which I have stored in another table.

我正试图让它们显示在树状结构中，如下所示:

I am trying to get them to display in a tree structure like so:

一个夜晚

• 俱乐部和社会
• 公共房屋
• 餐馆
• 出租车和私家车
• 剧院和音乐厅
• 酒吧

住宿

• 床和早餐
• 宾馆
• 假日住宿
• 酒店
• 自助式住宿

农业

• 农业机械及配件
• 农业商人
• 动物饲料
• 乡村装
• 奶制品

等

目前，我可以创建以下内容:

At the moment I am able to create the following:

使用此代码:

$dbc = mysql_connect($db_host,$db_user,$db_pass);
$sdb = mysql_select_db($db_database);

$query = 'SELECT category_name, subcategory_name FROM categories, subcategories WHERE subcategory_parent = category_name';

$result = mysql_query($query, $dbc)
or die (mysql_error($dbc));

while($row = mysql_fetch_array($result)) {

$catname = $row["category_name"];
$subcatname = $row["subcategory_name"];

echo "<li>$catname</li><ul><li>$subcatname</li></ul>";
}

我想让第一级类别仅显示一次，并且其子类别在它们下方的列表中.谁能告诉我最有效的方法吗?我想我需要使用foreach，但不确定.

I want to get the first level category to display only once with the subcategories in a list below them. Can anyone tell me the most efficient way to do this? I think I need to use foreach but am not sure.

我建立的第三级类别表具有与该表相同的结构，但是它是subsubcategory_id/subsubcategory_parent/subsubcategory_name.

The third level category table I have set up has the same structure as this table but is subsubcategory_id / subsubcategory_parent / subsubcategory_name.

推荐答案

仅在catname更改时输出.您还需要先按category_name排序查询.

only output the catname when it changes. You will also need to order your query by category_name first.

$row = mysql_fetch_array($result);
$catname = $row["category_name"];
$subcatname = $row["subcategory_name"];
$last = $catname;

echo "<li>$catname</li><ul>"

while($row = mysql_fetch_array($result)) {
    $catname = $row["category_name"];
    $subcatname = $row["subcategory_name"];
    if($last != $catname){
        echo "</ul><li>$catname</li><ul>"
    }
    echo "<li>$subcatname</li>";
    $last = $catname;
}
echo "</ul>";

只需完全重新阅读该问题，然后想说，关于分层树，使用父/子(或类别/子/子子)不是最好的方法.尽管它确实有效，但通常需要多个查询和递归函数才能显示.一种更好的方法是使用嵌套集，它正是为此目的而制作的.

Just re-read the question fully and want to say that when it comes to hierarchical trees, using a parent/child (or category/sub/subsub) is not the best method. Although it does work, it usually requires multiple queries and recursive functions for display. A better approach is to use the nested set which is made for exactly this purpose.

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