Re: Best way to "and" from a one-to-many joined table? - Mailing list pgsql-sql

Hi,

This is how I do it, and it runs fast:

select p.*
from test_people p inner join test_attributes a on p.people_id = 
a.people_id
where a."attribute" = @firstAttr or a."attribute" = @secondAttr

If you have many attributes to search for you can replace the where part 
with

where a."attribute" in (@firstAttr,@secondAttr,...)

For best results, you can index the field "attribute" on test_attributes 
table. Be aware of case sensitivity of PG text search.

Best regards,

Milan Oparnica


Oliveiros Cristina wrote:
> Howdy, Bryce
>  
> Could you please try this out and tell me if it gave what you want.
>  
> Best,
> Oliveiros
>  
> SELECT person_name
> FROM test_people p
> JOIN test_attributes a
> ON ((a.people_id = p.people_id) AND (a."attribute" = @firstAttr))
> JOIN test_attributes b
> ON ((b."people_id" = p."people_id") AND (b."attribute" = @secondAttr));
> 
>     ----- Original Message -----
>     *From:* Bryce Nesbitt <mailto:bryce2@obviously.com>
>     *To:* sql pgsql <mailto:pgsql-sql@postgresql.org>
>     *Sent:* Friday, December 05, 2008 6:55 PM
>     *Subject:* [SQL] Best way to "and" from a one-to-many joined table?
> 
>     Dear Experts,
> 
>     I'm looking for a good technique to do "and" searches on one-to-many
>     joined tables.  For example, to find people with both 'dark hair'
>     and 'president':
> 
>     # select * from test_people join test_attributes using (people_id);
>     +-----------+-------------+---------------+
>     | people_id | person_name |   attribute   |
>     +-----------+-------------+---------------+
>     |        10 | Satan       | The Devil     |
>     |         9 | Santa       | Imaginary     |
>     |         8 | Obamba      | Dark Hair     |
>     |         8 | Obamba      | Dark Hair     |
>     |         8 | Obamba      | USA President |
>     |        10 | Satan       | Dark Hair     |
>     +-----------+-------------+---------------+
> 
>     # select person_name from test_people where people_id in
>     (select people_id from test_attributes where attribute='USA President' 
>      INTERSECT
>      select people_id from test_attributes where attribute='Dark Hair');
> 
>     # select person_name from test_people
>     where people_id in
>     (select people_id from test_attributes where attribute='USA President')
>     and people_id in
>     (select people_id from test_attributes where attribute='Dark Hair');
> 
>     # select people_id,count(*) as count from test_people
>     join test_attributes using (people_id)
>     where attribute='Dark Hair' or attribute='USA President'
>     group by people_id having count(*) >= 2;
> 
> 
>     A postgres specific solution is OK, but SQL92 is better.  I had the
>     "in" solution recommended to me, but it's performing dramatically
>     poorly on huge tables.
> 
>     Thanks for any references to a solution!  -Bryce