任何人都知道如何修复此C ++以尝试将从MySQL数据库返回的行打印到文本文件（.txt）

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

我对C ++很新,所以我不确定。

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.

该应用程序的基本目标是允许用户输入SQL查询,然后将数据库中的结果行返回到文本(.txt)文件。

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

这是前面的部分和int Main()的变量

#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

这是导致程序崩溃的问题的代码段,但我不知道是什么导致它崩溃

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";
     }

1 个解决方案

#1

row = mysql_fetch_row(res);

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

到目前为止的所有内容看起来都不错,但是您将行视为字符串:

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:

那是错的。您的尾随+“\ t \ t”和您的奇怪“”+(不要这样做; C ++不是JavaScript)可能正在执行越界指针算法。如果您已正确完成流式传输:

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

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

那么我想你的编译器会更好地警告你不能用这种方式处理行。

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.

手册中有一个如何使用MYSQL_ROW的例子。提示:这是一个数组;结果集中每列(或“字段”)的一个元素。

#1

row = mysql_fetch_row(res);