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Message-ID: <bf05e51c0609091026r77ba3973hcd1d73556723a5a6@mail.gmail.com>
Date: Sat, 9 Sep 2006 12:26:10 -0500
From: "Aaron Bono" <postgresql@aranya.com>
To: emilu@encs.concordia.ca
Subject: Re: Is it possible to left join based on previous joins result
Cc: pgsql-sql@postgresql.org
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On 9/7/06, Emi Lu <emilu@encs.concordia.ca> 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.



the syntax is
LEFT JOIN [table] AS ...

you have b.col2 which means the database will interpret col2 as the table
name and subsequently b as the schema name

You should have
SELECT a.*
FROM a
INNER JOIN b using(col2)
LEFT JOIN b as c on (c.col1 = a.col1)

In the "using(col2)", what columns and tables are you joining there?  I
always dislike that syntax as it is ambiguous in some cases and not very
easy to read.

==================================================================
   Aaron Bono
   Aranya Software Technologies, Inc.
   http://www.aranya.com
   http://codeelixir.com
==================================================================

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On 9/7/06, <b class="gmail_sendername">Emi Lu</b> &lt;<a href="mailto:emilu@encs.concordia.ca">emilu@encs.concordia.ca</a>&gt; wrote:<div><span class="gmail_quote"></span><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
I tried the example as the following:<br><br>create table a(col1);<br>create table b(col1, col2)<br><br>select a.*<br>from a inner join b using(col2)<br>left join b.col2 as c on (c.col1 = a.col1)<br><br>System notifies me that b is not a schema name.
<br><br>So, I guess the approach that I tried to do is not acceptable by Pgsql<br>grammar.</blockquote><div><br>&nbsp;</div>the syntax is<br>LEFT JOIN [table] AS ...<br><br>you have b.col2 which means the database will interpret col2 as the table name and subsequently b as the schema name
<br><br>You should have <br>SELECT a.*<br>FROM a<br>INNER JOIN b using(col2)<br>LEFT JOIN b as c on (c.col1 = a.col1)<br><br>In the &quot;using(col2)&quot;, what columns and tables are you joining there?&nbsp; I always dislike that syntax as it is ambiguous in some cases and not very easy to read.
<br></div><br>==================================================================<br>&nbsp;&nbsp; Aaron Bono<br>&nbsp;&nbsp; Aranya Software Technologies, Inc.<br>&nbsp;&nbsp; <a href="http://www.aranya.com">http://www.aranya.com</a><br>&nbsp;&nbsp; <a href="http://codeelixir.com">
http://codeelixir.com</a><br>==================================================================

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