CODEWITHSUNDEEP
c++mysqldatabase
Jay1995
Jay1995

Reputation: 147

Anyone know how I can fix this C++ for trying to print the rows returning from a MySQL Database into a Text File(.txt)

I'm very new to C++ so I'm not sure.

The Basic aim of the application is to allow the user to enter an SQL Query and then return the rows of results from the database to a text(.txt) file.

Here is part before and the variables for the int Main()

#include <iostream>
#include <string>
#include <windows.h>
#include <mysql.h>
#include <fstream>

using namespace std;

int main(int argc, char** argv)
{
    MYSQL* conn;
    MYSQL_ROW row;
    MYSQL_RES *res;
    unsigned int num_rows;
    unsigned int ii;
    int qstate;

This is the code segment that keeps causing the problem of making the program crash but I just cant figure out whats causing it to crash

if(!qstate)
{
     res = mysql_store_result(conn);
     cout<<"Enter File Name: "<<endl;
     std:string FileName;
     std::getline(cin, FileName);

     string FN = ""+FileName+".txt";

     const char* fileN = FN.c_str();

     ofstream theSaveFile(fileN, ios::app);

     num_rows = mysql_num_rows(res);
     row = mysql_fetch_row(res);

     for(ii = 0; ii < num_rows; ii++)
     {
         if(!theSaveFile)
         {
             cout<<"Printing to the file failed"
             <<endl;
             exit(1);
         }
         theSaveFile<<""+row+" \t\t";
     }

Upvotes: 0

Views: 244

Answers (1)

Lightness Races in Orbit
Lightness Races in Orbit

Reputation: 385194

row = mysql_fetch_row(res);

Everything up until now looks ok, but then you treat row as a string:

theSaveFile<<""+row+" \t\t";

That's just wrong. Your trailing +" \t\t" and your strange ""+ (don't do this; C++ is not JavaScript) are probably performing out-of-bounds pointer arithmetic. If you'd done streaming properly:

theSaveFile << row << " \t\t";

then I imagine your compiler would be better placed to warn you that row cannot be treated this way.

There's an example in the manual of how to use MYSQL_ROW. Hint: it's an array; one element for each column (or "field") in your resultset.

Upvotes: 2

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