title: display the subcategory data also on submit main category query in php
body: <p>I have created a website where i have put category in three levels like 
  Main category -> sub category -> sub sub category</p>
  
  <p>and this category i used in adding product whatever category i selected from the list each product have get in to that category. Now i am trying to display the products category wise on my site there i have put a list buttons where i have display all the category and sub categories now the problem is that when i m going to click on main category it displays only those products which are having that category selected but i want to display the subcategory also if a main category clicks, here is the query:</p>
  
  <pre><code>SELECT * FROM `products` WHERE `product_category`='$_REQUEST[cat]' ORDER BY `product_id` DESC
  </code></pre>
  
  <p>in this query the request cat is the name of the category which i got on page.</p>
  
  <p>i want to know the query which display the sub category also if a main category is clicked</p>