When grilled further on (Mon, 12 Jan 2004 07:28:09 +0100),
Tomasz Myrta <[EMAIL PROTECTED]> confessed:

> Dnia 2004-01-12 05:04, Użytkownik Robert Creager napisał:
> > 
> > SELECT date_trunc( 'hour', "when" )::timestamp AS
> > period FROM readings WHERE period NOT IN (SELECT "time" FROM
> > hour.summary_period) GROUP BY period ORDER BY period;
> > 
> > The error is:
> > 
> > ERROR:  column "period" does not exist
> > 
> Your problem has nothing to "NOT IN".
> Your query works fine, when you remove column alias from WHERE clause - 
> it's beacause WHERE clause is executed *before* data output (and before 
> column aliases). You can still use column aliases in "GROUP BY" and 
> "ORDER BY".

Thanks for the info.

So now I have:

SELECT p.period FROM (SELECT date_trunc( 'hour', "when" )::timestamp AS period
FROM readings GROUP BY period) AS p WHERE p.period NOT IN (SELECT "time" FROM
hour.summary_period) ORDER BY p.period;

which appears works as expected.  Anything obviously goofy with the above query?

Cheers,
Rob
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