mysql_free_result()函数的作用是释放结果集的内存，是同步的，也就是要中断一下

该实验使用了MySQL链接数据库的基本使用方法，具体使用了

MYSQL_RES 数据库的mysql_store_result()函数的返回值是一个结果集，该函数的作用是检索比并存储整个结果集

MYSQL_ROW 数据库的mysql_fetch_row()函数的返回值是一个集行，搭配上一个mysql_res使用的，一个一个读他，函数的作用是获取下一个结果集行

mysql_query()函数是执行语句的意思，也就是发给数据库让他执行这条语句，函数传递语句的使用如果是std::string 类型的话，需要调用.c_str()函数进行转化成字符才能进行传递

std::ifstream  infile("../src/student2.txt",std::ios::in);
infile>>temp[j];

std::ofstream outfile("../src/student2.txt",std::ios::out);
outfile<<"学号\t"<<"名字\t"<<"得分\n"<<std::endl;

该方法分别对应了流对于文件的读入和写入操作的执行，使用完毕之后要执行close()操作

本实验我认为最重要的是对于mysql的链接建立问题

    MYSQL mysql;const char db_Username[]="root";const char db_Password[]="123456";const char db_Host[]="localhost";const char db_Name[]="sp";unsigned long db_Port=3306;mysql_init(&mysql);mysql_options(&mysql,MYSQL_SET_CHARSET_NAME,"gbk");if(mysql_real_connect(&mysql,db_Host,db_Username,db_Password,db_Name,db_Port,NULL,0)==NULL){std::cout<<"connect error!!!"<<std::endl;return false;}std::cout<<"connect success!!!"<<std::endl;

1. build
2. docs
3. include
   1. Main.h
   2. Student.h
4. src
   1. main.cpp
   2. Methods.cpp
   3. student.cpp
   4. student2.txt
5. CMakeLists.txt

Main.h

#ifndef NEW_PROJECTS_MAIN_H
#define NEW_PROJECTS_MAIN_H#include<iostream>
#include<mysql.h>
#include <fstream>void show_mean();//显示菜单bool connect_mysql(MYSQL& mysql);//链接数据库void query(MYSQL& mysql);//查询学生数据void modify(MYSQL& mysql);//修改学生数据void insert(MYSQL& mysql);//添加学生数据void Delete(MYSQL& mysql);//删除学生数据void filein(MYSQL& mysql);//导入文件数据int getline();//获取文件行数void fileout(MYSQL& mysql);//将数据库中的文件导出到另外一个文件中void createTable(MYSQL& mysql);//创建表格#endif //NEW_PROJECTS_MAIN_H

Student.h

#ifndef NEW_PROJECTS_STUDENT_H
#define NEW_PROJECTS_STUDENT_H
#include"main.h"
class Student{
private:int Id;std::string name;int score;
public:int getId();std::string getName();int getScore();void setId(int& Id);void setName(std::string& name);void setScore(int& score);
};
#endif //NEW_PROJECTS_STUDENT_H

main.cpp

#include "Main.h"int main() {MYSQL mysql;mysql_init(&mysql);mysql_options(&mysql,MYSQL_SET_CHARSET_NAME,"gbk");system("chcp 65001");if(connect_mysql(mysql)==false){return 0;}else{int choices=1;while(choices!=0){show_mean();std::cin>>choices;switch (choices) {case 1:filein(mysql);break;case 2:query(mysql);break;case 3:modify(mysql);break;case 4:insert(mysql);break;case 5:Delete(mysql);break;case 0:fileout(mysql);break;default:std::cout<<"Input error,please again!!!"<<std::endl;break;}}std::cout<<"success"<<std::endl;system("pause");system("cls");}}

Methods.cpp

#include"Main.h"
#include"Student.h"
void show_mean() // 展示功能菜单并让用户选择功能
{std::cout << std::endl << "=========================================欢迎使用学生管理系统========================================" << std::endl << std::endl;;std::cout << "请选择您要进行的操作" << std::endl;std::cout << "\t 1. 读取学生数据并显示" << std::endl;std::cout << "\t 2. 查询学生数据" << std::endl;std::cout << "\t 3. 修改学生数据" << std::endl;std::cout << "\t 4. 添加学生数据" << std::endl;std::cout << "\t 5. 删除学生数据" << std::endl;std::cout << "\t 0. 退出管理系统" << std::endl;}
void create_table(MYSQL& mysql){char Quest[]= "CREATE TABLE IF NOT EXISTS `Student1`(\`Id` int AUTO_INCREMENT,\`name` varchar(20),\`score` double,\PRIMARY KEY (`Id`)\)ENGINE=InnoDB DEFAULT CHARSET=utf8;";int re=mysql_query(&mysql,Quest);if(re==0)std::cout<<"table already"<<std::endl;
}bool connect_mysql(MYSQL& mysql){const char db_Username[]="root";const char db_Password[]="123456";const char db_Host[]="localhost";const char db_Name[]="sp";unsigned long db_Port=3306;mysql_init(&mysql);mysql_options(&mysql,MYSQL_SET_CHARSET_NAME,"gbk");if(mysql_real_connect(&mysql,db_Host,db_Username,db_Password,db_Name,db_Port,NULL,0)==NULL){std::cout<<"connect error!!!"<<std::endl;return false;}std::cout<<"connect success!!!"<<std::endl;create_table(mysql);return true;
}
int getline(){int len=0;std::ifstream infile("../src/student2.txt",std::ios::in);char c;
//    if (!infile.is_open()) {
//        std::cerr << "Error: Unable to open file. ";
//        std::cerr << "Error code: " << errno << std::endl;
//        return -1; // 或者其他适当的错误码
//    }while(infile.get(c)){
//        if(c=='\n')len++;len++;std::cout<<c;}infile.close();std::cout<<"data_len is "<<len-1<<std::endl;return len;
}void filein(MYSQL& mysql){int n=getline();std::cout<<"already student data:"<<std::endl;mysql_options(&mysql,MYSQL_SET_CHARSET_NAME,"gbk");std::ifstream  infile("../src/student2.txt",std::ios::in);const int N=300;const int N2=100;std::string temp[N];Student* student=new Student[N2];int x=0;int tempId;int tempScore;if(!infile.is_open()){std::cout<<"file open errr!!!"<<std::endl;exit(0);}else{char line[256]={0};int i=0;while(!infile.eof()&&i<N){for(int j=i;j<i+3;j++){infile>>temp[j];std::cout<<"\t\t"<<temp[j]<<"\t";}std::cout<<std::endl;tempId=atoi(temp[i].c_str());tempScore=atoi(temp[i+2].c_str());student[x].setId(tempId);student[x].setName(temp[i+1]);student[x].setScore(tempScore);x++;i=i+3;}infile.close();}std::cout<<"insert into student1 table"<<std::endl;for(int i=1;i<x;i++){std::string sql = "insert into Student1 values (" + std::to_string(student[i].getId()) + "," + "'" + student[i].getName() + "'" + "," + std::to_string(student[i].getScore()) + ")";std::cout<<sql<<std::endl;mysql_query(&mysql,sql.c_str());}delete[] student;
}void fileout(MYSQL& mysql){MYSQL_RES* res;MYSQL_ROW row;std::ofstream outfile("../src/student2.txt",std::ios::out);mysql_query(&mysql,"select * from student1 order by Id");res= mysql_store_result(&mysql);std::cout<<"data:"<<std::endl;std::cout<<"学号\t"<<"名字\t"<<"得分\n"<<std::endl;outfile<<"学号\t"<<"名字\t"<<"得分\n"<<std::endl;while(row= mysql_fetch_row(res)){std::cout<<"\t"<<row[0]<<"\t\t"<<row[1]<<"\t\t"<<row[2]<<std::endl;outfile << row[0] << "\t" << row[1] << "\t" << row[2] << std::endl;}std::cout << "他们将被保存到../src/student2.txt中" << std::endl;outfile.close();mysql_free_result(res);
}void query(MYSQL& mysql) // 查询学生数据
{MYSQL_RES* res; // 创建一个结果集MYSQL_ROW row; // 二维数组存放记录std::cout << "您选择了查询学生信息" << std::endl;std::cout << "请输入您要查询的选项" << std::endl;std::cout << "\t 1. 查询全部学生" << std::endl;std::cout << "\t 2. 按学号查询" << std::endl;std::cout << "\t 3. 按照名字进行查询" << std::endl;std::cout << "\t 4. 按照分数进行查询" << std::endl;std::cout << "\t 5.自定义SQL命令进行查询" << std::endl;int choice;std::string sql;std::cin >> choice;switch (choice) {case 1:{std::cout << "全体学生信息如下：" << std::endl;sql = "select * from student1 order by Id";std::cout << "查询的SQL语句如下：" << std::endl << sql << std::endl; // 检查语句mysql_query(&mysql, sql.c_str());break;}case 2:{std::cout << "请输入要查询的学生学号" << std::endl;int Id;std::cin >> Id;sql = "select * from student1 where Id = " + std::to_string(Id) + " order by Id";std::cout << "查询的SQL语句如下：" << std::endl << sql << std::endl; // 检查语句mysql_query(&mysql, sql.c_str());break;}case 3:{std::cout << "请输入要查询的学生姓名" << std::endl;std::string name;std::cin >> name;sql = "select * from student1 where name = '" + name + "' order by Id";std::cout << "查询的SQL语句如下：" << std::endl << sql << std::endl; // 检查语句mysql_query(&mysql, sql.c_str());break;}case 4:{std::cout << "请输入要查询的学生分数" << std::endl;int score;std::cin >> score;sql = "select * from student1 where score = " + std::to_string(score) + " order by Id";std::cout << "查询的SQL语句如下：" << std::endl << sql << std::endl; // 检查语句mysql_query(&mysql, sql.c_str());break;}case 5:{std::cout << "请输入SQL命令语句" << std::endl;std::cin.ignore(1024, '\n');getline(std::cin, sql);std::cout << "查询的SQL语句如下：" << std::endl<< sql << std::endl; // 检查语句mysql_query(&mysql, sql.c_str());break;}default:std::cout << "输入有误请重试" << std::endl;}std::cout << "\t\t查询结果如下" << std::endl;res = mysql_store_result(&mysql); // 将查询得到的数据存入结果集if (res == NULL)std::cout << "所有学生均与你查询的数据不匹配" << std::endl;else {std::cout << "\t学号\t" << "\t姓名\t" << "\t得分\t" << std::endl;while (row = mysql_fetch_row(res)){std::cout << "\t" << row[0] << "\t\t" << row[1] << "\t\t" << row[2] << std::endl;}}mysql_free_result(res);
}void modify(MYSQL& mysql) // 修改学生数据
{int choice;int Id;std::string name;int score;std::string sql1;std::string sql2;std::string sql;MYSQL_RES* res;MYSQL_ROW row;std::cout << "您选择了修改学生信息" << std::endl;std::cout << "请输入您要修改的学生的信息及数据" << std::endl;std::cout << "\t 1. 按学号修改" << std::endl;std::cout << "\t 2. 按名字修改" << std::endl;std::cin >> choice;switch (choice){case 1:{std::cout << "请输入要修改的学生学号" << std::endl;std::cin >> Id;sql = "select * from student1 where Id = " + std::to_string(Id) + " order by Id";// sql = "select * from student1 where Id =" + to_string(Id);mysql_query(&mysql, sql.c_str());res = mysql_store_result(&mysql);row = mysql_fetch_row(res);if (row == NULL){std::cout << "不存在该学号的学生" << std::endl;break;}elsestd::cout << "请输入修改之后的学生姓名" << std::endl;std::cin >> name;std::cout << "请输入修改之后的学生分数" << std::endl;std::cin >> score;sql1 = "update Student1 set name= '" + name + "' where Id=" + std::to_string(Id);sql2 = "update Student1 set score= " + std::to_string(score) + " where Id=" + std::to_string(Id);std::cout << "修改的的SQL语句如下：" << std::endl << sql1 << std::endl << sql2 << std::endl; // 检查语句mysql_query(&mysql, sql1.c_str());mysql_query(&mysql, sql2.c_str());break;}case 2:{std::cout << "请输入要修改的学生姓名" << std::endl;std::cin >> name;sql1 = "select * from Student1 where name ='" + name + "'";mysql_query(&mysql, sql1.c_str());res = mysql_store_result(&mysql);row = mysql_fetch_row(res);if (row == NULL){std::cout << "不存在该姓名的学生" << std::endl;break;}elsestd::cout << "请输入修改之后的学生学号" << std::endl;std::cin >> Id;std::cout << "请输入修改之后的学生分数" << std::endl;std::cin >> score;sql1 = "update Student1 set Id= " + std::to_string(Id) + " where name='" + name + "'";sql2 = "update Student1 set score= " + std::to_string(score) + " where name='" + name + "'";std::cout << "修改的的SQL语句如下：" << std::endl << sql1 << std::endl << sql2 << std::endl; // 检查语句mysql_query(&mysql, sql1.c_str());mysql_query(&mysql, sql2.c_str());break;}default:std::cout << "输入有误请重试" << std::endl;}//mysql_free_result(res);
}void insert(MYSQL& mysql)//添加学生信息
{int Id;std::string name;int score;MYSQL_RES* res; // 创建一个结果集MYSQL_ROW row; // 二维数组存放记录std::string sql1;std::string sql2;std::cout << "您选择了添加学生信息" << std::endl;std::cout << "请输入学生学号" << std::endl;std::cin >> Id;sql1 = "select * from student1 where Id = " + std::to_string(Id) + " order by Id";mysql_query(&mysql, sql1.c_str());res = mysql_store_result(&mysql);row = mysql_fetch_row(res);if (row != NULL)std::cout << "已存在该学号的学生，系统不允许学号相同，请重新添加或选择修改该学生信息" << std::endl;else {std::cout << "请输入学生名字" << std::endl;std::cin >> name;std::cout << "请输入学生得分" << std::endl;std::cin >> score;sql2 = "insert into Student1 values (" + std::to_string(Id) + "," + "'" + name + "'" + "," + std::to_string(score) + ")";std::cout << "插入的SQL语句如下：" << std::endl << sql2 << std::endl; // 检查语句mysql_query(&mysql, sql2.c_str());// 使用sql命令对数据库进行数据添加}mysql_free_result(res);
}
void Delete(MYSQL& mysql) // 删除学生数据
{int choice = 1;int Id;std::string name, sql1, sql2;int score;MYSQL_RES* res;MYSQL_ROW row;std::cout << "您选择了删除学生信息" << std::endl;//std::cout << "请输入您要删除的学生信息" << std::endl;std::cout << "\t 1. 按学号删除" << std::endl;std::cout << "\t 2. 按名字删除" << std::endl;std::cout << "\t 3. 按照分数删除" << std::endl;std::cin >> choice;switch (choice) {case 1:{std::cout << "请输入该生学号" << std::endl;std::cin >> Id;sql1 = "select * from Student1 where Id =" + std::to_string(Id);mysql_query(&mysql, sql1.c_str());res = mysql_store_result(&mysql);row = mysql_fetch_row(res);if (row == NULL){std::cout << "不存在该学号的学生" << std::endl;break;}elsesql2 = "delete  from Student1 where Id= " + std::to_string(Id);std::cout << "删除的SQL语句如下：" << std::endl << sql2 << std::endl; // 检查语句mysql_query(&mysql, sql2.c_str());break;}case 2:{std::cout << "请输入该生姓名" << std::endl;std::cin >> name;sql1 = "select * from Student1 where name ='" + name + "'";mysql_query(&mysql, sql1.c_str());res = mysql_store_result(&mysql);row = mysql_fetch_row(res);if (row == NULL){std::cout << "不存在该姓名的学生" << std::endl;break;}elsesql2 = "delete  from Student1 where name= '" + name + "'";std::cout << "删除的SQL语句如下：" << std::endl << sql2 << std::endl; // 检查语句mysql_query(&mysql, sql2.c_str());break;}case 3:{std::cout << "您确定要使用分数来删除信息吗，该操作可能会影响多名学生" << std::endl;std::cout << "1.确定\t 2.取消" << std::endl;int c = 0;std::cin >> c;if (c != 1){std::cout << "您选择了取消操作" << std::endl; break;}elsestd::cout << "您依旧选择了使用分数删除信息！" << std::endl;std::cout << "请选择要删除的分数" << std::endl;std::cin >> score;sql1 = "select * from Student1 where score =" + std::to_string(score);mysql_query(&mysql, sql1.c_str());res = mysql_store_result(&mysql);row = mysql_fetch_row(res);if (row == NULL){std::cout << "不存在该分数的学生" << std::endl;break;}elsesql2 = "delete  from Student1 where score= " + std::to_string(score);std::cout << "删除的SQL语句如下：" << std::endl << sql2 << std::endl; // 检查语句mysql_query(&mysql, sql2.c_str());break;}default:std::cout << "您输入的选项有误，请重新输入" << std::endl;}
}

Students.cpp

#include "Student.h"
int Student::getId() {return Id;
}
std::string Student::getName() {return name;
}
int Student::getScore() {return score;
}
void  Student::setId(int &id) {Id=id;
}
void Student::setName(std::string& Name) {name=Name;
}
void Student::setScore(int &Score) {score=Score;
}

student2.txt

学号 姓名 成绩
21 张三 98
22 李四 45

CMakeLists.txt

cmake_minimum_required(VERSION 3.20)
project(new_projects)set(CMAKE_CXX_STANDARD 17)include_directories(include)include_directories(D:/develop/MySQL/MySQL\ Server\ 8.0/include)
link_directories(D:/develop/MySQL/MySQL\ Server\ 8.0/lib)
link_libraries(libmysql)aux_source_directory(src DIR_SRCS)add_executable(new_projects ${DIR_SRCS})

AUTO_INCREMENT是主键，主键具有唯一性