Subject: Re: Is it possible to left join based on previous joins
From: Ragnar <gnari@hive.is>
To: emilu@encs.concordia.ca
Cc: pgsql-sql@postgresql.org
In-Reply-To: <45002689.9050307@encs.concordia.ca>
References: <45001AF6.4020706@encs.concordia.ca>
	<45002689.9050307@encs.concordia.ca>
Content-Type: text/plain
Date: Thu, 07 Sep 2006 14:30:50 +0000
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On fim, 2006-09-07 at 10:02 -0400, Emi Lu wrote:
> I tried the example as the following:
> 
> create table a(col1);
> create table b(col1, col2)
> 
> select a.*
> from a inner join b using(col2)
> left join b.col2 as c on (c.col1 = a.col1)
> 
> System notifies me that b is not a schema name.
> 
> So, I guess the approach that I tried to do is not acceptable by Pgsql 
> grammar.

it seems to me that basically you want to
select from a table whose name is stored in another
table.

one way to do that would be to use plpgsql or
some other procedural language to create
a set returning function, so that you
could do:
SELECT * from selfromtab('sometable');

after that is done,you might be able to use that
in joins

gnari


> 
> 
> > 
> > Is it possible to do something like:
> > 
> > select ...
> > from t1
> > inner join t2 ...
> > left join t2.colN
> > 
> > When t1 inner join with t2 I got unique result for t2.colN( colN's value 
> > is table name).
> > 
> > Can I continue to left join with the column "colN" in table t2?
> > 
> > Thanks
> > 
> > 
> > 
> > 
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