From: Gregory Stark <stark@enterprisedb.com>
To: "Tom Lane" <tgl@sss.pgh.pa.us>
Cc: "Michael Meskes" <meskes@postgresql.org>,
	"PostgreSQL Interfaces" <pgsql-interfaces@postgresql.org>
Subject: Re: PQprepare question
In-Reply-To: <17526.1178888881@sss.pgh.pa.us> (Tom Lane's message of "Fri, 11
	May 2007 09:08:01 -0400")
Organization: EnterpriseDB
References: <20070511111647.GA18711@feivel.credativ.de>
	<17526.1178888881@sss.pgh.pa.us>
Date: Fri, 11 May 2007 14:32:22 +0100
Message-ID: <87ps571o61.fsf@oxford.xeocode.com>
User-Agent: Gnus/5.110006 (No Gnus v0.6) Emacs/21.4 (gnu/linux)
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii

"Tom Lane" <tgl@sss.pgh.pa.us> writes:

> Michael Meskes <meskes@postgresql.org> writes:
>> According to the docs parameters are referenced as $1, $2, and so. Is
>> there a reason not to use "?" as placeholder?
>
> It's an operator name.

Most drivers such as JDBC and DBD::Pg do allow you to use ? parameters because
they're the ODBC standard. But they're just replacing them with $1 and so on
behind your back. If you want your code to be portable to other databases then
it makes sense to use ? 

But otherwise there are a few advantages to using $1, $2... a) You can change
your query to possibly use the arguments in a different order without having
to change the execute parameters as well. b) You can use a parameter multiple
times in a query without having to burden your execute call site with multiple
copies of the parameter.

I think you lose if you have an operator ? and want to use these drivers
though. Even if you only use $n parameters the driver may still get confused.
(At the very least if you ever have a query with no parameters and a ?
operator in it). 

-- 
  Gregory Stark
  EnterpriseDB          http://www.enterprisedb.com