var list = from t in db.tbl1s
            join t0 in db.tbl2s
                    on new 
                    { 
                        t.first_amount, 
                        t.second_amount, 
                        Column1 = t.first_amount, 
                        Column2 = t.second_amount, 
                        Column3 = (int?)t.trade_date.Value.Day,
                        Column4 = (int?)t.trade_date.Value.Month, 
                        Column5 = (int?)t.trade_date.Value.Year 
                    }
                equals new 
                {
                    t0.first_amount, 
                    t0.second_amount,
                    Column1 = t0.second_amount,
                    Column2 = t0.first_amount, 
                    Column3 = (int?)t0.trade_date.Value.Day, 
                    Column4 = (int?)t0.trade_date.Value.Month, 
                    Column5 = (int?)t0.trade_date.Value.Year } 
            into t0_join

            from t0 in t0_join.DefaultIfEmpty()

            select new
            {
                Column1 = a,
                Column2 = b,
                Column3 = c,
                Column4 = d,
            };