Обсуждение: select tbl1.attr1, number of tuples where tbl2.attr1=tbl1.attr1

Hey,

I have three tables.

table persons
{  login,  person_id UNIQUE
}

table views
{  person_id,  timestamp
}

table partners
{  person_id UNIQUE,  domain
}

for each tuple in partners i want to know the number of tuples in views with the same person_id.

I tried sth like
select partners.person_id, count(views.person_id) from partners, views where views.person_id = partners.person_id
but it said, partners.person_id must be grouped.

Then i tried
select partners.person_id, count(views.person_id) from partners, views where views.person_id = partners.person_id group
byviews.person_id
 

but this gave very strange results which are definitely not what i wanted.

How can I do that?

TIA, 
Markus Bertheau
Cenes Data GmbH


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Greetings,

I've been on this list for just a couple of days now; and I've seen the
word 'tuple' here a couple of times.

Excuse my lack my 'database'-jargon, but what is a 'tuple'?

Cheerio! Kr. Bonne.
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"Markus Bertheau" <twanger@eudoramail.com> writes:
> Then i tried
> select partners.person_id, count(views.person_id) from partners, views where views.person_id = partners.person_id
groupby views.person_id
 

> but this gave very strange results which are definitely not what i wanted.

I think you mistyped, because that query will also fail:

regression=# create table views (person_id int, timestamp timestamp);
CREATE
regression=# create table partners (person_id int UNIQUE, domain text);
NOTICE:  CREATE TABLE/UNIQUE will create implicit index 'partners_person_id_key' for table 'partners'
CREATE
regression=# select partners.person_id, count(views.person_id)
regression-# from partners, views where views.person_id = partners.person_id
regression-# group by views.person_id;
ERROR:  Attribute partners.person_id must be GROUPed or used in an aggregate function

How about showing us what you *really* did?
        regards, tom lane

Its a row. 

http://www.ca.postgresql.org/docs/faq-english.html#4.18

On Fri, 22 Jun 2001, Kristoff Bonne wrote:

> Greetings,
> 
> I've been on this list for just a couple of days now; and I've seen the
> word 'tuple' here a couple of times.
> 
> Excuse my lack my 'database'-jargon, but what is a 'tuple'?
> 
> Cheerio! Kr. Bonne.
>