如何在magento中将目录搜索更改为Like关键字搜索

In my magento store catelog search is working with given keyword but i want a like key word search which can help to users can search a product with a single letter For example Now my product sku like RAK22055

Now it allowing users to search only with RAK22055 But my requirement is users can search with 'A'

If users search with 'A' if should show the products whose containing 'A' in their SKU

I have checked all configurations in catalog

store>>configuration>>catalog search \