linux Ubuntu下，第一个C++程序访问数据库，遇到的问题，及解决办法

在ubuntu下安装了mysql，mysql++以后，编写了第一个访问数据库的程序：

cpp 复制代码

#include <iostream>
#include <string>
#include <cstdlib> //for system
#include <mysql++.h>

using namespace std;

int main()
{
    mysqlpp::Connection con(false);
    con.set_option(new mysqlpp::SetCharsetNameOption("gbk"));
    cout << "please input (user root) password: ";
    string pwd;
    getline(cin, pwd);

    if(!con.connect("d2school", "localhost", "root", pwd.c_str()))
    {
        cout << "can't connect database, please check the password!" << endl;
        return -1;
    }

    mysqlpp::Query query = con.query("select * from user");
    mysqlpp::StoreQueryResult res = query.store();

    for(unsigned int i = 0; i < res.num_rows(); ++ i)
    {
        cout << res[i]["name"] << endl;
    }

    return 0;
}

结果运行时报错：

运行时的日志信息如下：

-------------- Run: Debug in HelloDatabase_Console (compiler: GNU GCC Compiler)---------------

Checking for existence: /home/yanzhenxi/BaiHuaC++/chap04/HelloDatabase_Console/bin/Debug/HelloDatabase_Console

Set variable: LD_LIBRARY_PATH=.:/usr/lib/x86_64-linux-gnu

:/usr/local/lib:

Executing: gnome-terminal -t HelloDatabase_Console -x /usr/bin/cb_console_runner LD_LIBRARY_PATH=:.:/usr/lib/x86_64-linux-gnu

:/usr/local/lib /home/yanzhenxi/BaiHuaC++/chap04/HelloDatabase_Console/bin/Debug/HelloDatabase_Console (in /home/yanzhenxi/BaiHuaC++/chap04/HelloDatabase_Console/.)

Process terminated with status 0 (0 minute(s), 3 second(s))

我以为，是libmysql++-dev没有安装，所以

sudo apt install libmysql++-dev

结果依然是：

我的codeblocks中Global variable配置如下：

工程HelloDatabase_Console的build options如下：

再经过一顿操作之后,问题依然不能解决：

解决方案：

把下面图片中的 $(#mysql.lib)移到$ (#mysqlpp.lib)下方，或者删除掉，就可以了

第一种方案：把**$(#mysql.lib)移动到下方**

这种情况下，运行时信息如下：

-------------- Run: Debug in HelloDatabase_Console (compiler: GNU GCC Compiler)---------------

Checking for existence: /home/yanzhenxi/BaiHuaC++/chap04/HelloDatabase_Console/bin/Debug/HelloDatabase_Console

Set variable: LD_LIBRARY_PATH=.:/usr/local/lib:/usr/lib/x86_64-linux-gnu

Executing: gnome-terminal -t HelloDatabase_Console -x /usr/bin/cb_console_runner LD_LIBRARY_PATH=:.:/usr/local/lib:/usr/lib/x86_64-linux-gnu

/home/yanzhenxi/BaiHuaC++/chap04/HelloDatabase_Console/bin/Debug/HelloDatabase_Console (in /home/yanzhenxi/BaiHuaC++/chap04/HelloDatabase_Console/.)

Process terminated with status 0 (0 minute(s), 2 second(s))

运行结果为：

第二种方案：把**$(#mysql.lib)删掉**

第二种方案，运行时信息如下：

-------------- Run: Debug in HelloDatabase_Console (compiler: GNU GCC Compiler)---------------

Checking for existence: /home/yanzhenxi/BaiHuaC++/chap04/HelloDatabase_Console/bin/Debug/HelloDatabase_Console

Set variable: LD_LIBRARY_PATH=.:/usr/local/lib:

Executing: gnome-terminal -t HelloDatabase_Console -x /usr/bin/cb_console_runner LD_LIBRARY_PATH=:.:/usr/local/lib /home/yanzhenxi/BaiHuaC++/chap04/HelloDatabase_Console/bin/Debug/HelloDatabase_Console (in /home/yanzhenxi/BaiHuaC++/chap04/HelloDatabase_Console/.)

Process terminated with status 0 (0 minute(s), 2 second(s))

运行结果如下：

原因分析：

可以看到，这三种情况下的运行时信息的不同之处：

出错情况：

Set variable: LD_LIBRARY_PATH=.:/usr/lib/x86_64-linux-gnu
:/usr/local/lib:

Executing: gnome-terminal -t HelloDatabase_Console -x /usr/bin/cb_console_runner LD_LIBRARY_PATH=:.:/usr/lib/x86_64-linux-gnu

方案一：

Set variable: LD_LIBRARY_PATH=.:/usr/local/lib:/usr/lib/x86_64-linux-gnu
:

Executing: gnome-terminal -t HelloDatabase_Console -x /usr/bin/cb_console_runner LD_LIBRARY_PATH=:.:/usr/local/lib:/usr/lib/x86_64-linux-gnu

方案二：

Set variable: LD_LIBRARY_PATH=.:/usr/local/lib:

Executing: gnome-terminal -t HelloDatabase_Console -x /usr/bin/cb_console_runner LD_LIBRARY_PATH=:.:/usr/local/lib