Case expression on a created column

Question

I have set up a view in Microsoft SQL Server. The portion of the view which I am showing creates a column named Starch. How can I manipulate that created column within a case expression to decide if it is above or below 2?

.
..
...
MAX(CASE WHEN R.ANALYTE = 'Starch'  then 
(CASE WHEN ISNUMERIC(R.RN5) = 1 THEN CONVERT(float,R.RN5) ELSE convert(float,0) END)  end) as [Starch],

CASE 
WHEN Starch > 2 THEN 'ABOVE'
ELSE 'Below' END 
As 'Starch_Cautionary',
...
..
.

Answer 1

Assuming your ISNUMERIC still doesn't cause a conversion error (which it could depending on the data, even when it = 1) then you could wrap this in a CTE among other things.

with cte as(
.
..
...
MAX(CASE WHEN R.ANALYTE = 'Starch'  then 
(CASE WHEN ISNUMERIC(R.RN5) = 1 THEN CONVERT(float,R.RN5) ELSE convert(float,0) END)  end) as [Starch],
...
..
.)

select
   *,
   CASE 
   WHEN Starch > 2 THEN 'ABOVE'
   ELSE 'Below' END 
   As 'Starch_Cautionary',
...
..
.
from  cte

Example of ISNUMERIC() Failing... Sort of... Atleast for your case

declare @table table (i varchar(16))
insert into @table
values
('$'),
('1e4'),
('1,256,233'),
('5D105')

select isnumeric(i) from @table

These all return true, but would fail the convert...