如何让第一级类别只显示一次?

问题描述

我在mysql中设置了一个表，如下:

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 - 以及我存储在另一个表中的可能的第三级类别.

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.

我试图让它们显示在这样的树结构中:

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

一夜情

• 俱乐部和社团
• 公共房屋
• 餐厅
• 出租车和私人租用车辆
• 剧院和音乐厅
• 酒吧

住宿

• 民宿
• 旅馆
• 度假住宿
• 酒店
• 自助式住宿

农业

• 农业机械及备件
• 农商行
• 动物饲料
• 乡村服饰
• 乳制品

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>";
}

我想让第一级类别只显示一次，子类别在它们下面的列表中.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和这个表结构一样，但是是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

只在catname变化时输出.您还需要先按 category_name 对查询进行排序.

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>";

只需重新完整阅读问题并想说，当涉及到分层树时，使用父/子(或类别/子/子子)不是最好的方法.虽然它确实有效，但它通常需要多个查询和递归函数才能显示.更好的方法是使用专门为此目的而制作的 嵌套集.

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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