Query performance with functions

[Curt W. Zirzow]

Hello,

 I noticed that in the latest version of mysql that you no longer can 
use the column alias inside the where clause. Does this (ie. In the 
following query) cause the function be called in both cases or would 
it be called once and aliased in the where clause? 

select function(column) as column_alias
from table
where function(column) > 0

Curt.