Update tabel header dari tabel detail

UPDATE a 
 SET a.kolom_header = b.HRG 
 FROM tabel_header a
 INNER JOIN 
 ( 
    SELECT kode_id, SUM(trans_detail) AS HRG 
    FROM tabel_detail
    GROUP BY kode_id
 ) b ON a.kode_id = b.kode_id 
 [WHERE  (kondisi)]


Contoh :

update a
set a.totalqty = b.ttlqty
from jual_header a
inner join 
(
  select id, sum(trans_qty) as ttlqty
from jual_detail  group by id 
) b on a.id = b.id  where a.tgl between '2016-01-01' and '2016-01-05'