Reusing columns in SELECT list

Hello all.

Is there a way to reuse in the SELECT list columns defined earlier
in it ? With PostgreSQL 8.0, I couldn't manage to do it :

=> CREATE table a (x int);
CREATE TABLE
=> CREATE table b (y int);
CREATE TABLE
=> SELECT x * y AS xy, xy + xy AS twoxy FROM a, b;
ERROR: column "xy" does not exist

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André Majorel <URL:http://www.teaser.fr/~amajorel/>
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