Re: Outer Joins
От | Grant Finnemore |
---|---|
Тема | Re: Outer Joins |
Дата | |
Msg-id | 3A0004EA.3E7724F6@ucs.co.za обсуждение исходный текст |
Ответ на | Outer Joins ("Marc Rohloff" <Marc.Rohloff@eskom.co.za>) |
Список | pgsql-sql |
Marc, I did not look at your queries, but outer joins are supported in the latest development version of PostgreSQL, and will besupported in the upcoming 7.1 release of the software - beta due soon. Regards, Grant Marc Rohloff wrote: > I've been looking at the open-source databases for a project I am working on and while reading about Postgres I saw thatthey do not support outer joins yet. I was intrigued by their solution of using a union query. > > Something Like: > select a.col1, b.col2 from a,b where a.col1 = b.col2 > union > select a.col1, NULL from a where a.col1 not in (select b.col2 from b) > > But I was wondering if the following would work (it does in some other databases) > > select a.col1, b.col2 from a,b > where a.col1 = b.col2 > or b.col2 is null > > or maybe even > > select a.col1, b.col2 from a,b > where a.col1 = b.col2 > or a.col1 not in (select b.col2 from b) > > These would seem to be far more efficient than a union query > (I would try this but I don't have a Unix box at the moment to install PostgreSQL on!) > > Marc Rohloff -- > Poorly planned software requires a genius to write it > and a hero to use it. Grant Finnemore BSc(Eng) (mailto:gaf@ucs.co.za) Software Engineer Universal Computer Services Tel (+27)(11)712-1366 PO Box 31266 Braamfontein 2017, South Africa Cell (+27)(82)604-5536 20th Floor, 209 Smit St., Braamfontein Fax (+27)(11)339-3421 Johannesburg, South Africa
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