php - 从sql数据库的类别列表中订购一组子类别

Question

我有这个代码，但我不知道如何订购我的查询

function get_All_Categories(){
//new instance of mysqli
    $mysqli = new mysqli(DB_SERVER, DB_USER, DB_PASSWORD, DB_NAME);
    //if it doesn't work give an error
    if (!$mysqli) {
        die('There was a problem connecting to the database.');
    }
    $queryCats ="SELECT Catid, Catname
                 FROM ProductCats
                 ORDER BY Catid";
    $querySubCats ="SELECT Subcatname, Parentid
                    FROM ProductSubCats, ProductCats
                    WHERE ProductSubCats.Parentid = ProductCats.Catid
                    ORDER BY Subcatname;";
    if ($catResults = $mysqli->query($queryCats)){
        if (!$catResults) {
            echo 'Could not run query: ' . mysql_error();
            exit;
        }
        else{
            $subCatResults = $mysqli->query($querySubCats);
        }
        while ($rows = $catResults->fetch_assoc()) {
            echo '<div class = "categoryCluster">';
            echo '<a href="../index.php?Cat='.$rows["Catname"].'">'.$rows["Catname"].'</a>';
            echo '<br>';
            while($rowsSub = $subCatResults->fetch_assoc()){
                echo '<div class="subCategoryCluster">';
                echo '&emsp;'.'<a href="../index.php?Cat='.$rows["Catname"].'&'.'Subcat='.$rowsSub["Subcatname"].'">'.$rowsSub["Subcatname"].'</a>';
                echo '<br>';
                echo '</div>';
            }
            echo '</div>';
        }
    }
    $mysqli->close();
}

显示此输出:

Header 1
 Subcat 1
 Subcat 2
 OtherSubcat 1
Header 2
Header 3
Header 4
Header 5
Header 6

但我的问题是subcat 1和subcat 2的parentid为1，符合header 1，而othersubcat 1的parentid为5。实际上符合header 5。是的，在我的循环中，它紧接着其他 2 个显示。

现在我知道为什么这是错误的了，这是因为 while 循环中的 while 循环命令它最后出现，并把它粘在那里。

但我完全不知道如何修改它以便显示:

Header 1
 Subcat 1
 Subcat 2
Header 2
Header 3
Header 4
Header 5
 OtherSubcat 1
Header 6

示例表:

>     ProductSubCats
>     Subcatid  |  Subcatname   | Parentid
>     1         | Subcat 1      | 1
>     2         | Subcat 2      | 1
>     3         | Othersubcat 3 | 5
> 
> 
> 
> ProductCats
>     Cat id   |   Catname
>     1        | Header 1
>     2        | Header 2
>     3        | Header 3
>     4        | Header 4
>     5        | Header 5
>     6        | Header 6

谢谢你的帮助

Answer 1

按照@Pasha Bitz 所说的，对于您正在尝试做的事情。

尝试以下操作:

$categories = array();
        $sub_categories = array();  
        while ($rows = $catResults->fetch_assoc()) {
            $categories[$rows['Catid']] = $rows['Catname'];
        }
        while($rows = $subCatResults->fetch_assoc()){
            if (!isset($sub_categories[$rows['Parentid']])) {
                $sub_categories[$rows['Parentid']] = array();
            }
            $sub_categories[$rows['Parentid']][] = $rows['Subcatname'];
        }
        foreach ($categories as $cat_id => $name) {
            echo '<div class = "categoryCluster">';
            echo '<a href="../index.php?Cat='.$name.'">'.$name.'</a>';
            echo '<br>';
            if (isset($sub_categories[$cat_id])) {
                foreach($sub_categories[$cat_id] as $cat_id => $sub_cat_name) {
                    echo '<div class="subCategoryCluster">';
                    echo '&emsp;'.'<a href="../index.php?Cat='.$name.'&'.'Subcat='.$sub_cat_name.'">'.$sub_cat_name.'</a>';
                    echo '<br>';
                }
            }
        }

这应该可以为您解决这个问题，研究代码以便您了解这里发生了什么。