Windows phone 7.5 DataBase

Question

I want to build an application on visual studio 2010 professional that have more than fifteen table with relations many-to-many,many-to-one,one-to-one....
now i will start programming my application on windows phone 7.5 using c#, and i see that i should use LINQ to Sql ,but what is the Database that i should use !!! ,and how can i see the database i mean the server like Sql server 2008, or like use the database in visual studio 2010 professional when create c3 windows application .....
i need help in how to start with the database on windows phone 7.5 .

Thanks all.