回覆: Re: A strange problem
От | Tang Tim Hei |
---|---|
Тема | 回覆: Re: A strange problem |
Дата | |
Msg-id | 20050828004656.JTUZ7605.wmail04dat.netvigator.com@mail.netvigator.com обсуждение исходный текст |
Ответы |
Re: 回覆: Re: A strange problem
Re: ?^???G Re: A strange problem |
Список | pgsql-general |
> > 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.
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