Communicating with PostgreSQL Using LibPQ - PostgreSQL Developer's Guide - page 186

conn = PQconnectdb(conninfo);
if (PQstatus(conn) == CONNECTION_BAD)
{
fprintf(stderr, "connection to database failed\n");
fprintf(stderr, "%s", PQerrorMessage(conn));
return -1;
}
/* Execute a query using PQexec */
result = PQexec(conn, "SELECT id, name FROM foo LIMIT 3");
if (result == NULL || PQresultStatus(result) != PGRES_TUPLES_OK)
{
fprintf(stderr, "failed to execute query using PQexec\n");
fprintf(stderr, "%s", PQerrorMessage(conn));
return -1;
}
ntuples = PQntuples(result);
fprintf(stdout, "%d tuples returns\n", ntuples);
for (i = 0; i < ntuples; i++)
{
char *id, *name;
int id_col = PQfnumber(result, "id");
int name_col = PQfnumber(result, "name");
if (id_col < 0 || name_col < 0)
{
fprintf(stderr, "invalid result\n");
break;
}
id = PQgetvalue(result, i, id_col);
name = PQgetvalue(result, i, name_col);
fprintf("Data: id = %s, name = %s\n", id, name);
}
PQfinish(conn);
return 0;
}