UPDATE TBLMUHFIS SET FIRMADOVTUT=(TBLMUHFIS.TUTAR/X.DBO.DOVIZ.DOV_ALIS)
INNER JOIN x.DBO.DOVIZ ON (x.DBO.DOVIZ.TARIH = TBLMUHFIS.TARIH)
WHERE X.DBO.DOVIZ.SIRA='1'
UPDATE TBLMUHFIS y SET y.FIRMADOVTUT = y.TBLMUHFIS.TUTAR / (SELECT DOV_ALIS FROM x.DBO.DOVIZ WHERE TARIH = y.TARIH AND SIRA = '1')
WHERE y.TARIH = (SELECT TARIH FROM x.DBO.DOVIZ WHERE TARIH = y.TARIH AND SIRA = '1')
UPDATE TBLMUHFIS
SET FIRMADOVTUT = round((TBLMUHFIS.TUTAR/X.DBO.DOVIZ.DOV_ALIS),2)
from TBLMUHFIS a, x.DBO.DOVIZ b
where b.TARIH = a.TARIH and b.SIRA='1'