1.Go to sql server and create a [VIEW] and join table's together.
2.Add View to LINQ to SQL
3.
DataClasses1DataContext db = new DataClasses1DataContext();
ViewNameBindingSource.DataSource = db.ViewName.Where(c => c.Name=="KeySearch").Select(c=>c);
2)Example By linq
var query = from p in db.QuizParticipants
join points in db.ParticipantPoints on p.id
equals points.participantId into participantsGroup
from po in participantsGroup
join winners in db.Winners on p.id
equals winners.participantId into winnersGroup
from w in winnersGroup
where p.hasAttended == 1 && p.weeknumber == weeknumber
select new
{
ParticipantId = p.id,
HasAttended = p.hasAttended,
Weeknumber = p.weeknumber,
UmbracoMemberId = p.umbMemberId,
Points = po.points,
HasWonFirstPrize = w.hasWonFirstPrize,
HasWonVoucher = w.hasWonVoucher
};