Re: ALL() question

Julien Cigar wrote:
> 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 ...

Not if you test for what you want too:

...
FROM foo
WHERE test_bit_id = ANY ('{1,3}')
...or...
WHERE test_bit_id IN (1,3)

> 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)

Yes, but that doesn't help with your query - one row can't match ALL 
your values.

--   Richard Huxton  Archonet Ltd