Case-insensitive advanced search in Rails model

How can I apply first example result to second example?

1) Case insensitive search result in Rails model

 self.where("LOWER(shop_name) like ?", "%#{search.downcase}%")

2) advanced search

shops =Shop.where("shop_name LIKE '%#{keywords}%' AND shop_city LIKE '%#{keywords2}%' AND shop_country LIKE '%#{keywords3}%' AND market_type LIKE '%#{keywords4}%'") if keywords||keywords2||keywords3||keywords4.present?