Many dialects already support using aliases in GROUP BY and HAVING too, btw. IMO it's most useful (though somewhat more difficult to implement) to be able to u

Many dialects already support using aliases in GROUP BY and HAVING too, btw. IMO it's most useful (though somewhat more difficult to implement) to be able to use the aliases with window functions or large case/when statements, something like SELECT page, SUM(clicks) AS total_clicks, 100. * total_clicks / (SUM(total_clicks) OVER ()) AS click_pct, 100. * SUM(total_clicks) OVER (ORDER BY total_clicks DESC ROWS BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW) / (SUM(total_clicks) OVER ()) AS cumulative_click_pct FROM weblog GROUP BY page;