From: Bart Degryse <Bart.Degryse@indicator.be>
To: pgsql-sql@postgresql.org
Subject: Re: ALL() question
Date: Wed, 14 Nov 2007 13:57:21 +0100
Message-ID: <473AFEC1.A3DD.0030.0@indicator.be> (raw)
In-Reply-To: <1195051800.3190.18.camel@frodon.be-bif.ulb.ac.be>
References: <1195047542.3190.9.camel@frodon.be-bif.ulb.ac.be>
<473AE27E.60501 03@archonet.com>
<1195051800.3190.18.camel@frodon.be-bif.ulb.ac.be>
The doc says "The right-hand side is a parenthesized subquery, which must return exactly one column..."
That's what you have if using "... where test_bit_id = all(select id from test_bits where id in (1,2,3,4));"
The doc continues "...The left-hand expression is evaluated and compared to each row of the subquery result using the given operator, which must yield a Boolean result ..."
So your where expression is equivalent to:
where test_bit_id = (select id from test_bits where id = 1) AND
test_bit_id = (select id from test_bits where id = 2) AND
test_bit_id = (select id from test_bits where id = 3) AND
test_bit_id = (select id from test_bits where id = 4);
The doc continues "... The result of ALL is "true" if all rows yield true ..."
Since test_bit_id can never be 1, 2, 3 and 4 at the same time the result of ALL will be false. So no records get returned.
>>> Julien Cigar <jcigar@ulb.ac.be> 2007-11-14 15:50 >>>
On Wed, 2007-11-14 at 11:56 +0000, Richard Huxton wrote:
> Julien Cigar wrote:
> >
> > What I would like is a query that returns all the specimen_id of
> > this table which have _all_ the given test_bit_id.
> [snip]
> > With the following I got a syntax error:
> > select specimen_id
> > from specimen_test_bits
> > where test_bit_id = all(1,2,3,4);
>
> It's expecting an array here. You'd have to write
> = all('{1,2,3,4}')
> But that would have the same problem as...
>
> > The following works but no rows are returned :
> > select specimen_id
> > from specimen_test_bits
> > where test_bit_id = all(select id from test_bits where id in (1,2,3,4));
>
> It's testing each row individually and of course one row can't match ALL
> four values.
>
> What you want to do is count the distinct values. Something like:
>
> SELECT
> specimen_id
> FROM foo
> GROUP BY
> specimen_id
> HAVING
> count(distinct test_bit_id) = 4
> ;
>
I don't think it would work, for example if I have:
specimen_id | test_bit_id
------------+------------
100 1
100 3
101 1
101 2
the test_bit_ids are parameters, so with the given test_bit_id 1,3 it
would return specimen_id 101 too, which I don't want ...
What I would like is the specimen_id which match _exactly_ the given
test_bit_ids, so it should return only 100 in this example ..
from the documentation ALL() can take a subquery too, not only an ARRAY
(http://www.postgresql.org/docs/8.2/static/functions-subquery.html)
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To: pgsql-sql@postgresql.org
Cc: Bart.Degryse@indicator.be
Subject: Re: ALL() question
In-Reply-To: <473AFEC1.A3DD.0030.0@indicator.be>
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