--> 测试数据：[tbl]
go
if object_id('[tbl]') is not null 
drop table [tbl]
go
create table [tbl](
[ID] int,
[guige] varchar(11),
[shuliang] numeric(5,3)
)
go
insert [tbl]
select 1,'1*5',5.2 union all
select 2,'1.0/5',3 union all
select 3,'1/5',5 union all
select 4,'2*5+3',8 union all
select 5,'(8-5)*3',-5.213


declare @minid int
declare @maxid int
select @minid=MIN(id) from tbl
select @maxid=max(id) from tbl

go
declare @sql varchar(max)
set @sql=''
declare @minid int
select @minid=MIN(ID) from tbl
declare @maxid int
select @maxid=max(ID) from tbl
declare @str varchar(1000)
set @str=''
while @minid<=@maxid
begin
select @str='('+[guige]+')' from tbl 
where ID=@minid
select @str='select id,guige,shuliang,'
+@str+'*[shuliang] as heji
from tbl where ID='+cast(@minid as varchar)
print @str
set @sql=@sql+' union all '+@str
set @minid=@minid+1
end
print @sql
set @sql=RIGHT(@sql,LEN(@sql)-10)
exec(@sql)

/*
id    guige    shuliang    heji
1    1*5    5.200    26.000000000
2    1.0/5    3.000    0.600000000
3    1/5    5.000    0.000000000
4    2*5+3    8.000    104.000000000
5    (8-5)*3    -5.213    -46.917000000
*/

------解决方案--------------------

SQL code

declare @T table (ID int,guige char(7),shuliang decimal(18,3))
insert into @T
select 1,'1*5',5.2 union all
select 2,'1.0/5',3 union all
select 3,'1/5',5 union all
select 4,'2*5+3',8 union all
select 5,'(8-5)*3',-5.213

select *,dbo.m_charcompute(guige+'*('+ltrim(shuliang)+')') as newcol
from @T
/*
ID          guige   shuliang                                newcol
----------- ------- --------------------------------------- ----------------------
1           1*5     5.200                                   26
2           1.0/5   3.000                                   0.6
3           1/5     5.000                                   1
4           2*5+3   8.000                                   34
5           (8-5)*3 -5.213                                  -46.917
*/


create function [dbo].[m_charcompute](@bds varchar(1000))
returns float
as
BEGIN
set @bds = replace(@bds,' ','')--去空格，免得麻烦。
declare @i int,@j int 
declare @c1 char(1),@c2 char(1),@c varchar(100)
declare @v1 float,@v2 float,@v float
declare  @t table(id int identity(1,1),s varchar(100))
declare  @s table(id int identity(1,1),s varchar(100))
declare  @sv table(id int identity(1,1),v float)

select @i = 0,@j = len(@bds),@c2 = '',@c = ''
while @i<@j
begin
 select @c1 = @c2,@i = @i+1
 select @c2 = substring(@bds,@i,1)
if charindex(@c2,'.0123456789') > 0 or (@c2 = '-' and @c1 in('','*','-','+','/','(')) 

 begin   select @c = @c + @c2   continue  end
 if @c <> ''  begin insert @t(s)  select @c select @c = '' end
 if charindex(@c2,')')>0
 begin 
   insert @t(s)  select s from @s where id > isnull((select max(id) from @s where s in('(')),0) order by id desc
   delete @s where id >= isnull((select max(id) from @s where s in('(')),0) 
   continue
 end
 if charindex(@c2,'+-)')>0
 begin 
   insert @t(s)  select s from @s where id > isnull((select max(id) from @s where s in('(')),0) order by id desc
   delete @s where id > isnull((select max(id) from @s where s in('(')),0) 
   if @c2 <> ')' insert @s(s) select @c2
   continue
 end
 if charindex(@c2,'*/')>0
 begin 
   insert @t(s)  select s from @s where id > isnull((select max(id) from @s where s in('(','+','-')),0) order by id desc
   delete @s where id > isnull((select max(id) from @s where s in('(','+','-')),0) 
   insert  @s select @c2
   continue
 end
 if charindex(@c2,'(')>0 insert  @s select @c2
e