PHP/MySQL 查询结果

Question

查询有问题..我的 wscategories 存储了在线商店的主要类别，我的 wssubcategories 表存储了带有名为“parentcategory”的外键的表的子类别。我正在尝试列出主要类别，子类别在 la 下:

上衣

T 恤

编织

毛衣

裤子

短裤

牛仔裤

我写的查询/结果如下:

$query = "SELECT DISTINCT a.categoryname AS maincategory, b.categoryname AS   
smallcategory FROM wscategories a, wssubcategories b WHERE a.SECTION = 'girls' AND  
b.parentcategory = a.id";
      $result = mysql_query($query) or die(mysql_error());
      while ($row = mysql_fetch_array($result))
      {

        echo $row['maincategory'];

        echo "<br/>";
        echo $row['smallcategory'];
        echo "<br/>";
      }

哪个返回:

上衣

T 恤

上衣

毛衣

上衣

编织

等等。我希望脚本只显示一次主类别，然后显示下面的子类别，而不是多次显示它。有什么帮助吗？

Answer 1

尝试这样的事情

// note we need to order by maincategory for this to work
//
$query = "SELECT DISTINCT a.categoryname AS maincategory, b.categoryname AS   
smallcategory FROM wscategories a, wssubcategories b WHERE a.SECTION = 'girls' AND  
b.parentcategory = a.id
ORDER BY maincategory ASC,
smallcategory ASC
";
      $result = mysql_query($query) or die(mysql_error());


      // keep track of previous maincategory
      $previous_maincategory = NULL;

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

        // if maincategory has changed from previouscategory then display it
        if ($previous_maincategory != $row['maincategory']) {
            echo $row['maincategory'];
        }

        echo "<br/>";
        echo $row['smallcategory'];
        echo "<br/>";

        // record what the previous category was
        $previous_maincategory = $row['maincategory'];
      }