回覆： Re: A strange problem

>
> 寄件者: Stephan Szabo <sszabo@megazone.bigpanda.com>
> 日期: 2005/08/27 星期六 下午 11:25:49 HKT
> 收件者: Tang Tim Hei <timheit@netvigator.com>
> 副本: pgsql-general@postgresql.org
> 主旨: Re: [GENERAL] A strange problem
>
> On Sat, 27 Aug 2005, Tang Tim Hei wrote:
>
> > Hi,
>
> >   I'm new to postgresql. Anytime I type the following command to the
> >   database to run, it give me no result record if table 'country' is
> >   empty but can get result if 'country' is not empty. Is this so
> >   strange?
>
> Not really. You're doing a cartesian join between test.currency and
> test.country.  If there are no rows in test.country, there are no rows in
> the output of the from clause.
>
> >   select A.* from test.currency A, test.country B where A.curr_cd='USD'
>
>
>

In the above command, I just add another table reference to it and it gives me two different results.
Even I add columns like B.* to it, it do the same things too. Is it not consistance?
In real world, I don't know the 'country' table is empty or not.
Sometime it is empty and sometime it is not empty, this will confuse me whether my program has bug or not.