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Date: Sat, 7 Jan 2006 11:44:56 +0200
From: Volkan YAZICI <yazicivo@ttnet.net.tr>
To: JiangWei <jw.pgsql@sduept.com>
Cc: pgsql-interfaces@postgresql.org
Subject: Re: HOWTO pass "default value" to PQexecParams?
Message-ID: <20060107094455.GA634@alamut>
References: <43BDC4EF.7090408@sduept.com>
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AFAIK, it's not possible to point the field's default value using a
special value in the related array member. Because, you cannot declare
any special value in the array: NULL will be treated as NULL and other
char values as is.

(Recommended.) Why don't you omit id in the target table fields?
For instance:

  sprintf(sql_cmd, "INSERT INTO test ("
                   (id_will_be_default) ? "" : "id, "
                   "name) VALUES ("
                   "...");
  PQexecParams(conn, sql_cmd, ...);

You can also learn the default value of the related field too. (For
more information, run psql with -E parameter and type \d <table>.)

Furthermore, it's possible to define a RULE like:

  ON INSERT
  IF NEW.id = 0
    USE DEFAULT

This will assume 0 as a reference to default value.


HTH.
Regards.


On Jan 06 09:16, JiangWei wrote:
> Create Table test (
>    id int4 not null,
>    name text default '<noname>'
> );
> 
> PQexec (conn, "INSERT INTO test(id, name) VALUES (100,default)" ); // OK.
> 
> PQexecParams (conn, "INSERT INTO test(id, name) VALUES ($1, $2)" ); // 
> $1=100, $2= ????