Re: need nelp with aggregate functions

Thank you all very much.
This "official" forum is really great.

2009/11/19 Oliveiros C, <oliveiros(dot)cristina(at)marktest(dot)pt>

> Howdy,
>
> It is quite simple, the joins you used would output a long list of
> pairs (client,computer), and, as many people has more than one computer,
> many clients will appear repeated, but the COUNT keyword will count them
> more than once though.
>
> The DISTINCT keyword prevents one client from appearing more than once...
>
> It's basically that...
>
> Hope this helped
>
> Best,
> Oliveiros
>
>
> ----- Original Message -----
> *From:* Another Trad <anothertrad(at)gmail(dot)com>
> *To:* Oliveiros C, <oliveiros(dot)cristina(at)marktest(dot)pt>
> *Cc:* pgsql-sql(at)postgresql(dot)org
> *Sent:* Wednesday, November 18, 2009 5:37 PM
> *Subject:* Re: [SQL] need nelp with aggregate functions
>
> ok, I did: SELECT count(DISTINCT c.cliente_id) as
> qtd_client,count(cm.cm_id) as qtd_computers
> GREAT. It works.
> Please, explain me why and how it works, I wanna learn and do by myself
> next time :)
>
>
> 2009/11/18 Oliveiros C, <oliveiros(dot)cristina(at)marktest(dot)pt>
>
>> Try substituting the SELECT count(c) as qtd_client,count(cm) as
>> qtd_computers
>>
>> by
>>
>> SELECT count( DISTINCT c.cliente_id) as qtd_client,count(/* put here the
>> primary key of the computer table */ ) as qtd_computers
>>
>> Then tell me if it output what you want
>>
>> Best,
>> Oliveiros
>>
>>
>> ----- Original Message -----
>> *From:* Another Trad <anothertrad(at)gmail(dot)com>
>> *To:* pgsql-sql(at)postgresql(dot)org
>> *Sent:* Wednesday, November 18, 2009 4:55 PM
>> *Subject:* [SQL] need nelp with aggregate functions
>>
>> The DB structure is in attachment.
>> I with the number of clients and the number of computers that have
>> processors with "manufacturer" = "INTEL" and "speed" = "2GB"
>> I am trying:
>>
>> select count(c) as qtd_client, count(cm) as qtd_computers
>>
>>
>> from cliente c
>> inner JOIN computer cm on (c.cliente_id = cm.cliente_id)
>> inner join processor p on (cm.processor_id = p.processor_id)
>> inner join speed s on (s.speed_id = p.speed_id)
>> INNER JOIN manufacturer m on (p.manufacturer_id=m.manufacturer_id)
>>
>>
>> where m.manufacturer = 'INTEL'
>> and s.speed = '2GB'
>>
>> but is not working
>> anyone can help me?
>>
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>