I use all Software from SUSE Linux 9.0. If I try to use connection parameters reading them at runntime I alwas have an accessviolation (Speicherzugriffsfehler) Reading the data from the mysql table is still done but with an (Speicherzugriffsfehler) at the end. Using srtcpy makes the problem. The commented version is ok.
#include <mysql/mysql.h>
#include <stdio.h>
#include <string.h>
#include <string>
#include <iostream>
using namespace std;

int main()
{
cout << "Hello World" << endl;
MYSQL *mysql;
MYSQL_RES *res;
MYSQL_ROW row;
char *query;
int t,r;
char* db="zahlen";
unsigned int error;



mysql=mysql_init(NULL);
if(!mysql_real_connect(mysql,"localhost","root","hase",db,0,NULL,0))
{
printf("Error connecting\n");
}else printf("Connected ... \n");


// # # # # # # # # # # # # # #
//query="select * from nummern";
strcpy(query,"select * from nummern");
cout << "strlen(query)=" << strlen(query) << endl;
for (int i=0;i<strlen(query)+10;i++)
{
cout << query[i];
}
cout << endl << "ende query[i]" << endl;
t=mysql_real_query(mysql,query,(unsigned int) strlen(query));
if(t)
{
printf("error quera");
}else printf("Query made \n");



res=mysql_use_result(mysql);

while (row=mysql_fetch_row(res))
{
for(t=0;t<mysql_num_fields(res);t++){
printf("%s ",row[t]);
}
printf("\n");
error = mysql_errno(mysql);
cout << "myFehler: " << error << endl;
}

}

char *query; /* and */ strcpy(query,"select * from nummern"); // erm...
you should first allocate a size of memory for (char *)query.
by using
query = new char[BUFSIZ]; // (++ version) or...
query = (char *)malloc(BUFSIZ * sizeof(char));