var data = (from a in db.StudentData
            join b in db.Contacts on a.SID equals b.SID
            join c in db.Addresses on a.SID equals c.SID
            join d in db.EntryQuals.DefaultIfEmpty() on a.SID equals d.SID
            where a.SID == searchTxt
                  select new
                    {
                        ID = a.SID,
                        Birthdate = a.BIRTHDTE,
                        FirstName = a.FNAMES,
                        PreviousName = a.PREVSURNAME,
                        EntryQualAwardID = d.ENTRYQUALAWARDID,
                        AwardDate = d.AWARDDATE
       }).ToList();