Correct. There is no row, but we are getting data in the non-existing
row.
So how do I file a bug report on this?

-----Original Message-----
From: firebird-support@yahoogroups.com
[mailto:firebird-support@yahoogroups.com] On Behalf Of Michael Ludwig
Sent: Tuesday, June 19, 2012 5:22 PM
To: firebird-support@yahoogroups.com
Subject: Re: [firebird-support] Left join and computed columns

Rick Debay schrieb am 19.06.2012 um 15:58 (-0400):

> Since TEST_TABLE is empty, the results should be NULL.
> Changing the query to 'SELECT *' return the one row in RDB$DATABASE,
> and the column TEST_TABLE.ID is NULL and the column
> TEST_TABLE.COMPUTED_COL is "FAILED".
> If TEST_TABLE is empty, how can anything result from a join?

Ah. You're expecting one row (because of the LEFT JOIN), but in that
row, which happens to have only one column, you're expecting all fields
from the right table to be NULL because there is no matching row for the
JOIN condition. And the COMPUTED column is sort of overriding the NULL.
Did I paraphrase your thoughts correctly?

I have no idea what's the correct behaviour here. -- Michael

> > CREATE TABLE TEST_TABLE
> > (
> > ID INTEGER,
> > COMPUTED_COL VARCHAR(6) COMPUTED BY ('FAILED') );
> >
> > SELECT t.COMPUTED_COL
> > FROM RDB$DATABASE r
> > LEFT JOIN TEST_TABLE t
> > ON r.RDB$RELATION_ID = t.ID
> >
> > COMPUTED_COL
> > ------------
> > FAILED

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