title: How would you create a clothing size db structure?
body: <p>I need to design a structure for clothing sizes on an e-commerce site.<br>
  We are using mysql</p>
  
  <p>For now, we have something like this:</p>
  
  <pre><code>product(product_id, name, size_id)  
  (12, 'formal shoes', 2)  
  (224, 'pants', 16)  
  
  size(size_id, gender, category_id)  
  (2, 'm', 5)  
  (16, 'm', 8)  
  (17, 'm', 8)  
  (18, 'm', 8)  
  
  category(category_id, category_name)  
  (5, 'shoes'),  
  (8, 'pants')
  
  size_chart(size_id, country_code, value)  
  (2, 'US', '7')  
  (2, 'UK', '5')  
  (16, 'US', '33w34l')  
  (17, 'US', '33w32l')  
  (18, 'US', '33')  
  (16, 'EU', '48')  
  (17, 'EU', '48')  
  (18, 'EU', '48')  
  </code></pre>
  
  <p>Now, as you can see the problem is that EU 48 has 3 US equivalents (and they're different in the US), so it would be a mess to sort/filter based on a EU input size.<br>
  I noticed that many online shops got this wrong and they either leave the conversion to the user or simply list every single international size for search/filters.</p>
  
  <p>So, for example, if the user search for US 33w34l pants, I'd like to show him pants where size_id is 16,17 or 18.</p>
  
  <p>How would you structure everything?</p>