To Maintain Custom Login and Social Login on Application

Question

I have developed a web Application in MVC 4 with backend as Sql Server. I have created Custom Login and throught that user Could fetch the application. Now requirement is that to add Social sit Logins as facebook,google,Linkedin, twitter etc.

 

I have doubt that how to maintain in database. Suppose I have created the facebook login and create API key for facebook then how to customize it into database. Means if wheather user come from social login or custom login.

 

The databse of mine is look like below.

UserId     Password 

 

1               ***********

2               ***********