USE tempdb
GO

declare @t table (code int, altcode int, m money)

insert @t (code,altcode,m)
values (1,11,15.10), (11,111,18),(111,1111,11.3)
	  ,(2,22,3),(22,222,100)
	  ,(3,null,15)

;with cte as
(
select code codeGlobal, altcode, m
from @t t
where not exists (select * from @t t2 where t.code=t2.altcode)
UNION ALL
select c.codeGlobal, t.altcode, t.m
from @t t
	 join cte c ON c.altcode=t.code
)
select codeGlobal, MAX(m)
from cte
group by codeGlobal

with cte as
(
select code codeGlobal, code, altcode, price
from _bmw t
where not exists (select * from _bmw t2 where t.code=t2.altcode)
UNION ALL
select c.codeGlobal, t.code, t.altcode, t.price
from _bmw t
	 join cte c ON c.altcode=t.code
)
update _bmw
set CodeGlobal = c.codeGlobal
from _bmw as t
inner join cte c on t.code=c.code
go

declare @t table (code int, altcode int, m money, maxm money, src_code int)

insert @t (code,altcode,m) values (1,11,15.10)
insert @t (code,altcode,m) values (11,111,18)
insert @t (code,altcode,m) values (111,1111,11.3)
insert @t (code,altcode,m) values (2,22,3)
insert @t (code,altcode,m) values (22,222,100)
insert @t (code,altcode,m) values (3,null,15)

-- вот дай дураку фантик

declare @rc int

update t set maxm = m, src_code = code
  from @t t;

set @rc = @@rowcount;

while @rc > 0
begin
  update t set maxm = tt.maxm, src_code = tt.src_code
    from @t t inner join @t tt on t.altcode = tt.code and tt.maxm > t.maxm;
  set @rc = @@rowcount;
end;

select * from @t;