CODEWITHSUNDEEP
c++mysqlmysql-connector
Damian Vu
Damian Vu

Reputation: 409

C++ Connector to MySQL

EDITED:

My Problem is the errors at the bottom of this post.

Heres my additional include directories

C:\Program Files\boost
C:\Program Files\MySQL\MySQL Connector C++ 1.1.3\include
C:\Program Files\MySQL\MySQL Server 5.6\include

Additional Library Directories

C:\Program Files\MySQL\MySQL Server 5.6\lib
C:\Program Files\MySQL\Connector C++ 1.1.2\lib\opt

Additional Dependencies

libmysql.lib
mysqlcppconn-static.lib

Heres my code

#include <iostream>
#include <cstdio>
#include <cstdlib>
using namespace std;

#include <stdlib.h>
#include <Windows.h>
#include <mysql.h>
#include "mysql_connection.h"

#include <cppconn/driver.h>
#define host "localhost"
#define username "root"
#define password "root"
#define database "tests"

int main()
{
    MYSQL* conn;
    conn = mysql_init( NULL );
    if( conn )
    {
        mysql_real_connect( conn, host, username, password, database, 0, NULL, 0 );
    }
    MYSQL_RES* res_set;
    MYSQL_ROW row;
    unsigned int i;
    mysql_query( conn, "SELECT * FROM tbl_clients WHERE id = 1" ); 
    res_set = mysql_store_result( conn );
    unsigned int numrows = mysql_num_rows( res_set ); 
    if( numrows )
    {
        row = mysql_fetch_row( res_set );
        if( row != NULL )
        {
            cout << "Client ID  : " << row[0] << endl;
            cout << "Client Name: " << row[1] << endl;
        }
    }
    if( res_set )
    {
        mysql_free_result( res_set );
    }
    if( conn )
    {
        mysql_close( conn );
    }

    return 0;
}

These are the errors I get

1>------ Build started: Project: okay, Configuration: Debug Win32 ------
1>welp.obj : error LNK2019: unresolved external symbol _mysql_num_rows@4 referenced in function _main
1>welp.obj : error LNK2019: unresolved external symbol _mysql_init@4 referenced in function _main
1>welp.obj : error LNK2019: unresolved external symbol _mysql_real_connect@32 referenced in function _main
1>welp.obj : error LNK2019: unresolved external symbol _mysql_query@8 referenced in function _main
1>welp.obj : error LNK2019: unresolved external symbol _mysql_store_result@4 referenced in function _main
1>welp.obj : error LNK2019: unresolved external symbol _mysql_free_result@4 referenced in function _main
1>welp.obj : error LNK2019: unresolved external symbol _mysql_fetch_row@4 referenced in function _main
1>welp.obj : error LNK2019: unresolved external symbol _mysql_close@4 referenced in function _main
1>C:\Users\Damian\documents\visual studio 2012\Projects\okay\Debug\okay.exe : fatal error LNK1120: 8 unresolved externals
========== Build: 0 succeeded, 1 failed, 0 up-to-date, 0 skipped ==========

Please help, This project is due in about 48 hours for my class, and I've spent so much time trying to figure this out.

Thanks

Upvotes: 2

Views: 7316

Answers (2)

Sanoob
Sanoob

Reputation: 2474

This is error is happening due to linker problem. The linker is not able to find the required static or dynamic libraries (mysql.lib,mysqlcppconn-static.lib,libmysql.dll and libmysql.lib). The additional lib setting is wrong. Check this site give the path correctly Building MySQL Connector/C++ Windows Applications with Microsoft Visual Studio

Upvotes: 1

Constantin
Constantin

Reputation: 17808

respectfully, your last two questions are compiler/linker questions. I understand your frustration, as I knew how to code early but knew nothing about compilers/linkers. When you get a moment take some time to read about:

  • headers
  • binary vs object file
  • libraries / shared object
  • compiler
  • linker
  • function mangling (C vs C++)

To answer your question, I am guessing you're doing this in Microsoft Visual Studio:

  1. You need to go to Project Properties and set Additional Library Paths (i see you did that from your last post)
  2. You need to specify the library, I'm going out on a limb here and assuming it will mysql.lib ... There's an "Additional Library" input somewhere in the Linker section, you'll be able to identify it because kernel32.lib will be int it. Add the mysql.lib to that section. Confirm the name by going to the mysql folder which holds the binaries.
  3. Make sure you're using the static library, the .dll will give you new issues that you don't need to worry about. This is usually achieved by setting the correct library directory. Many c++ libraries will ship with precompiled "Static" and "Dynamic" folders containing the correct libraries.

Upvotes: 2

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