SQL Server 2005 : Converting varchar value '1.23E-4' to decimal fails

declare @a varchar(40)
set @a='1.23e-4'
declare @b decimal(27,12)

if isnum开发者_如何转开发eric(@a) =1
begin

    select @b=cast(@a as decimal(27,12))

end
else
begin
    select @b=-1
end

select @b

when exeucting above sql code under SQL 2005 environment I am getting following error.

Error converting data type varchar to numeric

anyone knows why?

thanks.

---

SELECT  @b = CONVERT(REAL, @a, 2)

Scientific notation only works on FLOAT and REAL.

---

cast via float first.

SQL is quite strict about decimal

eg

SELECT CAST('' AS float), CAST('' AS int), CAST('' AS float) --0
SELECT CAST('' AS decimal) --error