根据类别从表中提取图像并停止重复的结果

Question

表 样本数据

壁

wall_id   wall_name
  1        wall_1
  2        wall_2
  6        wall_6

wall_categories

wall_id   category_id
  1           2
  2           1
  6           1
  6           2

类别

category_id  category_name
  1            Wallpaper
  2            Photography

HTML

<a href="file.php?sort=upload_date">Date</a>
<a href="file.php?sort=wall_views">Views</a>
<a href="file.php?sort=wall_downloads">Downloads</a>

<a href="file.php?filter=1">Wallpaper</a>
<a href="file.php?filter=2">Photography</a>

PHP

$sortBy = array('upload_date','wall_views','wall_downloads');
$sort = 'upload_date';
if(isset($_GET['sort']) && inarray($_GET['sort'], $sortBy)){
   $sort = $_GET['sort'];
}


$filterBy = array(1, 2);
$filter = join(',', $filterBy);
if(isset($_GET['sort']) && inarray($_GET['sort'], $sortBy)){
   $sort = $_GET['sort'];
}

我想拉 来自wall_id表的wall_name，wall_views，walls和基于category_name表的类别表中的wall_categories。以下是我得到的查询：

$walls_query = $connectDB->prepare("SELECT * FROM walls INNER JOIN wall_categories ON
                walls.wall_id = wall_categories.wall_id WHERE wall_categories.category_id  
                IN ($filter) AND walls.wall_id>? ORDER BY $sort DESC;");
     $query->execute();

这是使用wall_id

从数据库中选择类别的查询

$categories_query = $connectDB->prepare("SELECT category_name FROM categories INNER JOIN wall_categories 
    ON wall_categories.category_id = categories.category_id WHERE wall_id=?;");

问题是它会生成重复数据，有两个类别的图像会显示两次。需要阻止它。