implement AD authentication and verify user roles, department against a custom SQL DB

Hi All,

I have a  SP 2013  web appln, and we have external users also, as partners.

So for the internal users, we would like to implement  AD for authentication and once  the user logged in with AD credentials , we would like to authorize against a custom SQLDB. this  custom sql db has a table - sayuserInfoTable-  with columns  userRole, userDepartment etc.

assuming that according to the department created - Dept1,Dept2,Dept3 - these 3  site collections are  created in the web appln.

so once  the logged in user[ lets say user1 belongs to  Dept1 ] enters his/her credentials, he should navigate to the Dept1 site collection because his department is mentioned as Dept1 in the  userInfoTable.

any approaches for implementing this scenario is highly appreciated.

Because if  we assume that the AD doesnt have these  custom attributes like department, or roleinformation etc. so we  cant perform authorization with AD so  i am forced to perform authorization against this custom DB/userinfotable.

shankar