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* How to insert default value with libpq?
@ 2020-04-27 13:02 [email protected]
2020-04-28 14:25 ` Re: How to insert default value with libpq? Peter Eisentraut <[email protected]>
0 siblings, 1 reply; 3+ messages in thread
From: [email protected] @ 2020-04-27 13:02 UTC (permalink / raw)
To: [email protected]
Hello,
I would like to insert the default value for a field with libpq, but
inserting null or "default" doesn’t work.
I attached a simple example also available here
https://gitlab.com/snippets/1970590
Is it possible?
Attachments:
[text/x-csrc] main.c (988B, ../../[email protected]/2-main.c)
download | inline:
#include <stdio.h>
#include <stdlib.h>
#include "libpq-fe.h"
static void exec(PGconn* conn, const char* param)
{
const char* values[1] = {param};
PGresult* res = PQexecParams(
conn,
"INSERT INTO test (id) VALUES ($1);",
sizeof(values) / sizeof(*values),
NULL, // types
values,
NULL, // lengths
NULL, // formats
1
);
printf("%s", PQresultErrorMessage(res));
PQclear(res);
}
int main(int argc, char** argv)
{
const char* conninfo;
if (argc > 1) {
conninfo = argv[1];
} else {
conninfo = "host=localhost";
}
PGconn* conn = PQconnectdb(conninfo);
if (PQstatus(conn) != CONNECTION_OK)
{
fprintf(stderr, "Connection to database failed: %s", PQerrorMessage(conn));
exit(1);
}
PQexec(conn, "CREATE TEMPORARY TABLE test (id SERIAL PRIMARY KEY);");
exec(conn, NULL);
exec(conn, "default");
PQfinish(conn);
return 0;
}
^ permalink raw reply [nested|flat] 3+ messages in thread
* Re: How to insert default value with libpq?
2020-04-27 13:02 How to insert default value with libpq? [email protected]
@ 2020-04-28 14:25 ` Peter Eisentraut <[email protected]>
2020-04-29 10:59 ` Re: How to insert default value with libpq? [email protected]
0 siblings, 1 reply; 3+ messages in thread
From: Peter Eisentraut @ 2020-04-28 14:25 UTC (permalink / raw)
To: [email protected]; [email protected]
On 2020-04-27 15:02, [email protected] wrote:
> I would like to insert the default value for a field with libpq, but
> inserting null or "default" doesn’t work.
You cannot represent that using query parameters (PQexecParams). Query
parameters always mean, use this rather than the default value.
To do what you want either write DEFAULT or leave off the column
altogether, for example
INSERT INTO test (id) VALUES (DEFAULT)
but this needs to be pasted into the query string, not passed as a
parameter.
--
Peter Eisentraut http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
^ permalink raw reply [nested|flat] 3+ messages in thread
* Re: How to insert default value with libpq?
2020-04-27 13:02 How to insert default value with libpq? [email protected]
2020-04-28 14:25 ` Re: How to insert default value with libpq? Peter Eisentraut <[email protected]>
@ 2020-04-29 10:59 ` [email protected]
0 siblings, 0 replies; 3+ messages in thread
From: [email protected] @ 2020-04-29 10:59 UTC (permalink / raw)
To: [email protected]
Le 28/04/2020 à 16:25, Peter Eisentraut a écrit :
> but this needs to be pasted into the query string, not passed as a
> parameter.
Fine, thank you for your help!
^ permalink raw reply [nested|flat] 3+ messages in thread
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2020-04-28 14:25 ` Peter Eisentraut <[email protected]>
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