RE: [SQL] Why *no* ambig.uous complain in select part?

Поиск
Список
Период
Сортировка
От Edward W. Rouse
Тема RE: [SQL] Why *no* ambig.uous complain in select part?
Дата
Msg-id 018501c90497$d6c7f050$8457d0f0$@com
обсуждение исходный текст
Ответ на Why *no* ambig·uous complain in select part?  (Emi Lu <emilu@encs.concordia.ca>)
Ответы Re: RE: [SQL] Why *no* ambig.uous complain in select part?  (Emi Lu <emilu@encs.concordia.ca>)
Список pgsql-sql
Just a guess, but it seems to me that since the join is using col1 and col2
there is no ambiguity. They should be the same no matter which table it
comes from.

Edward W. Rouse


-----Original Message-----
From: pgsql-sql-owner@postgresql.org [mailto:pgsql-sql-owner@postgresql.org]
On Behalf Of Emi Lu
Sent: Friday, August 22, 2008 4:12 PM
To: pgsql-sql@postgresql.org
Subject: [SQL] Why *no* ambig.uous complain in select part?

Good morning,

Just notice one small thing, and need your information about select

select col1, col2
from table1
left join table2
using (col1, col2)

;

This query never complain about ambiguous columns of col1 and col2 in
the select part.

My guess is:
(1) col1, col2 always return table1.col1, table1.col2
(2) because using (col1, col2)
     that's why, table name is not necessary in select part

Am I wrong? Please advise?

Thank you!




--
Sent via pgsql-sql mailing list (pgsql-sql@postgresql.org)
To make changes to your subscription:
http://www.postgresql.org/mailpref/pgsql-sql



В списке pgsql-sql по дате отправления:

Предыдущее
От: Emi Lu
Дата:
Сообщение: Why *no* ambig·uous complain in select part?
Следующее
От: Emi Lu
Дата:
Сообщение: Re: RE: [SQL] Why *no* ambig.uous complain in select part?