Re: [gnome-db] gdaquery

["Vivien Malerba" <vmalerba gmail com>]

On 6/19/07, Andrea Zagli <azagli inwind it> wrote:
> i'm trying the new libgda-3
>
> my problem is that i didn't understand very well how gdaquery and gdaqueryfield joins together
>
> this is the code
>
> #include <libgda/libgda.h>
>
> int
> main (int argc, char **argv)
> {
>         GdaClient *client;
>         GdaConnection *conn;
>         GdaDict *dict;
>         GdaQuery *qu;
>         GdaObject *dm;
>         GError *error = NULL;
>
>         gda_init ("test", "1.0", argc, argv);
>
>         client = gda_client_new ();
>
>         conn = gda_client_open_connection_from_string (client, "SQLite", "DB_DIR=/media/disk/libgda3_gdaquery;DB_NAME=test.db", NULL, NULL, 0, &error);
>
>         if (conn == NULL)
>                 {
>                         g_fprintf (stderr, "Errore apertura connessione.\n%s\n", error->message);
>                 }
>         else
>                 {
>                         GdaQueryTarget *qutarget;
>                         GdaQueryField *qufield;
>                         GdaQueryField *quvalue;
>                         GValue *value;
>
>                         value = g_malloc0 (sizeof (GValue));
>
>                         error = NULL;
>                         dict = gda_dict_new ();
>                         gda_dict_set_connection (GDA_DICT (dict), conn);
>
>                         qu = gda_query_new (GDA_DICT (dict));
>                         if (qu == NULL)
>                                 {
>                                         g_fprintf (stderr, "Errore in gda_query_new.\n");
>                                 }
>
>                         gda_query_set_query_type (GDA_QUERY (qu), GDA_QUERY_TYPE_UPDATE);
>
>                         qutarget = gda_query_target_new (GDA_QUERY (qu), "appo");
>
>                         qufield = gda_query_field_field_new (GDA_QUERY (qu), "ciccio");
>                         gda_query_field_set_visible (GDA_QUERY_FIELD (qufield), TRUE);
>
>                         quvalue = gda_query_field_value_new (GDA_QUERY (qu), G_TYPE_STRING);
>                         g_value_init (value, G_TYPE_STRING);
>                         g_value_set_string (value, "paperino");
>                         gda_query_field_value_set_value (GDA_QUERY_FIELD_VALUE (quvalue), value);
>                         gda_query_field_set_visible (GDA_QUERY_FIELD (quvalue), TRUE);
>
>                         g_object_set (qufield,
>                                       "target", qutarget,
>                                       "target-id", "appo",
>                                       "target-name", "appo",
>                                       "value-provider", quvalue,
>                                       NULL);
>
>                         if (!gda_query_add_target (GDA_QUERY (qu), GDA_QUERY_TARGET (qutarget), &error))
>                                 {
>                                         g_fprintf (stderr, "Errore in add_target.\n%s\n", error->message);
>                                 }
>
>                         error = NULL;
>                         dm = gda_query_execute (GDA_QUERY (qu), NULL, FALSE, &error);
>                         if (error != NULL)
>                                 {
>                                         g_fprintf (stderr, "Errore in esecuzione query.\n%s\n", error->message);
>                                 }
>
>                         g_fprintf (stderr, "SQL: %s\n", gda_query_get_sql_text (GDA_QUERY (qu)));
>                 }
>
>
>         return 0;
> }
>
> when i execute it, it returns an error on gda_query_execute because the query's sql is wrong; in fact gda_query_get_sql_text returns "update appo set "
>
> instead I thought to have created "update appo set ciccio='paperino'"

You need to add the qufield and quvalue to the query, using
gda_entity_add(). I agree that it's not easy to find, and I probably
will add a gda_query_add_field() function in the future.

However, except for testing and learning purposes, I suggest you use
the gda_query_new_from_sql function which will do this for you in one
step.

Here is attached my modified version with some comments.

Regards,

Vivien

#include <libgda/libgda.h>

int
main (int argc, char **argv)
{
	GdaClient *client;
	GdaConnection *conn;
	GdaDict *dict;
	GdaQuery *qu;
	GdaObject *dm;
	GError *error = NULL;

	gda_init ("test", "1.0", argc, argv);

	client = gda_client_new ();

	conn = gda_client_open_connection_from_string (client, "SQLite", "DB_DIR=.;DB_NAME=Test.db", NULL, NULL, 0, &error);

	if (conn == NULL) {
		g_fprintf (stderr, "Errore apertura connessione.\n%s\n", error->message);
	}
	else {
		GdaQueryTarget *qutarget;
		GdaQueryField *qufield;
		GdaQueryField *quvalue;
		GValue *value;

		value = g_malloc0 (sizeof (GValue));

		error = NULL;
		dict = gda_dict_new ();
		gda_dict_set_connection (GDA_DICT (dict), conn);

		qu = gda_query_new (GDA_DICT (dict));
		/* REM: qu wil _never_ be NULL at this point, so no need to test it */
		if (qu == NULL)	{
			g_fprintf (stderr, "Errore in gda_query_new.\n");
		}

		gda_query_set_query_type (GDA_QUERY (qu), GDA_QUERY_TYPE_UPDATE);

		/* target */
		qutarget = gda_query_target_new (GDA_QUERY (qu), "appo");
		if (!gda_query_add_target (GDA_QUERY (qu), GDA_QUERY_TARGET (qutarget), &error)) {
			g_fprintf (stderr, "Errore in add_target.\n%s\n", error->message);
			g_error_free (error);
			error = NULL;
			exit (1);
		}
		g_object_unref (qutarget); /* don't forget to unref at this point unless you really want to keep
					      a reference on the object */

		/* ciccio field */
		qufield = gda_query_field_field_new (GDA_QUERY (qu), "ciccio");
		gda_query_field_set_visible (GDA_QUERY_FIELD (qufield), TRUE);
		gda_entity_add_field (GDA_ENTITY (qu), GDA_ENTITY_FIELD (qufield));
		g_object_unref (qufield);/* don't forget to unref at this point unless you really want to keep
					      a reference on the object */

		/* value field */
		quvalue = gda_query_field_value_new (GDA_QUERY (qu), G_TYPE_STRING);
		gda_query_field_set_visible (GDA_QUERY_FIELD (quvalue), FALSE);
		gda_entity_add_field (GDA_ENTITY (qu), GDA_ENTITY_FIELD (quvalue));
		g_object_unref (quvalue);/* don't forget to unref at this point unless you really want to keep
					      a reference on the object */

		g_value_init (value, G_TYPE_STRING);
		g_value_set_string (value, "paperino");
		gda_query_field_value_set_value (GDA_QUERY_FIELD_VALUE (quvalue), value);

		g_object_set (qufield,
			      "target", qutarget,
			      "target-id", "appo",
			      "target-name", "appo",
			      "value-provider", quvalue,
			      NULL);


		dm = gda_query_execute (GDA_QUERY (qu), NULL, FALSE, &error);
		if (error != NULL) {
			g_fprintf (stderr, "Errore in esecuzione query.\n%s\n", error->message);
		}

		g_fprintf (stderr, "SQL: %s\n", gda_query_get_sql_text (GDA_QUERY (qu)));
	}


	return 0;
}