E-commerce products filter

Question

Im trying to biuld a filter algorithm for my product list.

For example I have 2 Televisions.

First one is: screen Size 117 Cm, brand Samsung. Second one is: screen size 203 CM, brand Sharp.

And i have the following filters:

Brand: Samsung, Sharp

Screen size: 117 Cm, 203 CM

If I want to see only Samsung TVs and I check the Samsung Filter, how can I reach to conclusion that I should remove Screen size 203 from filters, because samsung have only 117 cm tv.

But if i check sharp tv and samsung in the same time, then I should see both screen size filters.

I m asking for an idea for some php/mysql algorithm.

I hope you understand what im asking.

For an example look here: http://www.ebay.co.uk/sch/Televisions-/11071/i.html?_dcat=11071&Display%2520Technology=LED%2520LCD&rt=nc

The website knows how many products it has have before user checks any filter: eg: "40" - 49" (326)) -> they know that they have 326 products before user checks that filter.

In short : The checkboxes you check in the filters, should be disabled if the combination is not available for the products.

I have 3 tables: products(id_product,name), filters(id_filter,name,id_category), filters_values(id,id_product,id_filter,value)

In my product_list page it should appear only filter that once being checked they return products.

My first thought is to make sql from each filter value combination. Eg 10 filters with 4 values: 40 sql, just to check if filters return products, But this is way to much stress on db

For example if I have one filter with 4 values, i should make 4 query in order to see if I have products on specific value.

I i have 10 filter each having 4 values i should do 40 sql query. Which is a lot. How can i do this faster?

Thanks

Answer 1

I usually do something like this in php:

 // queries all products if no filter are specified
$sql_query = "SELECT * FROM products ";


// add fileters e.g. from $_GET array
$i = 0;
foreach($filter_array as $filter -> $filter_value)
{
   if( ! $i)
   {
      $sql_query .= "WHERE ";
   }
   else
   {
      $sql_query .= " AND ";
   }

   $sql_query .= $fliter . " = '" . $filter_value . "'";

   $i++;       
}

// generating something like:
// "SELECT * FROM products WHERE color = 'green' AND brand = 'samsung'"
// now execture $sql_query

This is just a sketch but I think you get the idea