What are the major differences between Credit rating and Investment Banking?

Refer

http://www.huffingtonpost.com/vivian-norris-de-montaigu/the-difference-between-in_b_92446.html

Credit rating aims at measuring the credit worthiness of a firm or a country or institution or an individual. 

Investment Banking is with a much wider scope. Investment Bankers undertake Equity Research, Valuation of companies for Mergers & Acquisitions, Investment decisions in various asset classes such as stocks, bonds, etc.