I always seem to end up in a position where I need more specific information from a collection than addFilter() can give me. Functions like addAttributeToFilter() are great if you’re working with EAV-based collections like products and categories, but they don’t work with a lot of core Magento collections. In this post I’ll go into some detail on how to use the ->getSelect() function to filter collection results. This post comes with a warning: The methods detailed below are intended primarily for data output, not data manipulation. Be careful saving models returned from your original collection.

Calling $collection->getSelect() on your collection will return a model of class typeVarien_Db_Select. This model represents the SQL query that is performed to select your collection. I’ve created a module called Mby_Testmodule, and within it I have a model of typetestmodule/comment. Let’s get the Select element and play with it a bit.

Magento Provides the Web Services API Features to allow other systems to communicate with the magento store.
If you are new to magento webservices please visit the official site links

• Web Services Information
  
• Magento Core API

While there are methods available to fetch product from outside magento.
But there is no example given on the official site on how to use the method catalog.product_list with Filters.
Recently while Working with this Method I got unexpected results, either