wrong return value by mysql_num_fields in C++

Question

thanks for u r reply please give your reply for below program.

For table creation and insertion i am using these string.

Create table mystudents(sname varchar(50),sno varchar(25),mark1 numeric,mark2 numeric); insert into mystudents values('lala','tk001',100,100);

VC+++

---

CString("select * from mystudents;") int status = mysql_query(hnd,sql); if (status) { printf("Could not execute statement(s)"); mysql_close(hnd); //exit(0); } int lIntRow=0; MYSQL_RES *result=NULL; MYSQL_ROW row; // one row returned int numfield=0; // process each statement result

  result = mysql_store_result(hnd);
  if (result)
  {
 // yes; process rows and free the result set 
 //process_result_set(hnd, result);
        if (result) 
  {
   row = mysql_fetch_row(result); 
   numfield = mysql_num_fields(result); //wrong return value   
  }
  else
  {
   //fprintf(stderr,"Failed to use the result acquired!\n"); 
   return 0;
  }
  mysql_free_result(result);
  }
  else          // no result set or error
  {
 if (mysql_field_count(hnd) == 0)
 {
  printf("%lld rows affected\n",
   mysql_affected_rows(hnd));
 }
 else  // some error occurred
 {
   printf("Could not retrieve result set\n");
   break;
 }
  }

while i try to get details from table my using above VC++ code i am getting 1542852 or 14253689 values insteadof 1 from mysql_num_fields.

Answer 1

You should call mysql_free_result only after you are done with the result. In the loop you are iterating over memory that no longer represents the result data.