drop table if exists #TableA;
CREATE TABLE #TableA (value_day date, customer_id varchar(64), turn decimal(18,4));

INSERT #TableA (value_day, customer_id, turn) VALUES
(DATEFROMPARTS(2018,06,01) ,'customer1',500),
(DATEFROMPARTS(2018,06,02) ,'customer1',0),
(DATEFROMPARTS(2018,06,03) ,'customer1',11),
(DATEFROMPARTS(2018,06,04) ,'customer1',22),
(DATEFROMPARTS(2018,06,05) ,'customer1',33),
(DATEFROMPARTS(2018,06,06) ,'customer1',4),
(DATEFROMPARTS(2018,06,07) ,'customer1',0),
(DATEFROMPARTS(2018,06,08) ,'customer1',0),
(DATEFROMPARTS(2018,06,09) ,'customer1',0),
(DATEFROMPARTS(2018,06,10) ,'customer1',5),

(DATEFROMPARTS(2018,06,01) ,'customer2',6),
(DATEFROMPARTS(2018,06,02) ,'customer2',50),
(DATEFROMPARTS(2018,06,03) ,'customer2',448.55),
(DATEFROMPARTS(2018,06,04) ,'customer2',854.11),
(DATEFROMPARTS(2018,06,05) ,'customer2',59855),
(DATEFROMPARTS(2018,06,06) ,'customer2',45.22),
(DATEFROMPARTS(2018,06,07) ,'customer2',10),
(DATEFROMPARTS(2018,06,08) ,'customer2',0),
(DATEFROMPARTS(2018,06,09) ,'customer2',8),
(DATEFROMPARTS(2018,06,10) ,'customer2',99);
	
select *
from #TableA

<days>
  <d val="01.06.2018">500</d>
  <d val="02.06.2018">0</d>
  <d val="03.06.2018">11</d>
  ...
  <d val="10.06.2018">5</d>
</days>

select
 a.value_day, a.customer_id, a.turn, b.x as days_data
into
 #TableB
from
 (select min(value_day), customer_id, sum(turn) from #TableA group by customer_id) a(value_day, customer_id, turn) cross apply
 (select value_day as [@val], turn as [*] from #TableA where customer_id = a.customer_id for xml path('d'), root('days'), type) b(x);

select * from #TableA;
select * from #TableB;

select sum(datalength(value_day) + datalength(customer_id) + datalength(turn)) from #TableA;
select sum(datalength(value_day) + datalength(customer_id) + datalength(turn) + datalength(days_data)) from #TableB;

DATEFROMPARTS(2018,06,01)

'20180601'