Using column aliasses in the same query

Hi,

I am not sure if there ever was a feature request for using defined column aliases in the rest of a query.
This would make queries with a lot of logic in those aliased columns a lot smaller and this easier to write/debug.

I already know you can use the following syntax:

SELECT col1, col2, col3, (col2-col3) as col4 FROM (SELECT col1, (long and lots of logic here) as col2, col3 FROM table) s WHERE col2 < aValue

But when you need to use (calculated) values from the actual record and or have sub-selects in your main select that also need to use these values things get really hairy.
I don't know if the SQL specification allows it but I know that RDBMS's like Sybase already support this.

Any thoughts?

Cheers,
Robert