PHP / MySQL查询结果

Having an issue with a query..my wscategories stores the main categories of an online store, and my wssubcategories table stores the sub categories of the table with the foreign key called "parentcategory". I'm trying to list the main categories, with the subcategories underneath a la:

Tops

T-Shirts

Wovens

Sweaters

Pants

Shorts

Jeans

The query/result I wrote is the following:

$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/>";
      }

Which returns:

Tops

T-Shirts

Tops

Sweaters

Tops

Wovens

Etc. I want the script to just display the main category once, and then the subcategories underneath vs. displaying it multiple times. Any help?

try something like this

// 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'];
      }

Set a flag after you echo the main category, like this:

$echoed_main = false;
while ($row = mysql_fetch_array($result)) {
    if (!$echoed_main) {
        echo $row['maincategory'];
        echo "<br/>";
        $echoed_main = true;
    }
    echo $row['smallcategory'];
    echo "<br/>";
}