Re: ALL() question - Mailing list pgsql-sql

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)




---------------------------(end of broadcast)---------------------------
TIP 7: You can help support the PostgreSQL project by donating at

                http://www.postgresql.org/about/donate