mysql POS机的简单vs2013代码 及所遇问题解析

源码如下：

//user.h头文件

#include "windows.h"
#include "iostream"
#include "string.h"
#include "mysql.h"
using namespace std;


//货物的属性
struct Goods{//用结构体  还是用类啊？？
// Goods();
// ~Goods();
char* G_ID;
char* G_name;
char* G_amount;
char* G_selling_price;
char* manufacture;
char* discount;
};


/*普通用户的类*/
class Domestic{
public:
Domestic();
// ~Domestic();
char* putin(MYSQL*);//输入“ID”或“名字”，来返回一个字符串，
char* find(MYSQL*,int);//根据putin()的返回值 来找商品并显示
void inumber(MYSQL*);//输入数量,并打印总额
};


/*管理用户的类*/
class Manage :public Domestic{
public:
void add_Domestic(MYSQL*);
void del_Domestic(MYSQL*);
void add_Goods(MYSQL *);
void del_Goods(MYSQL *);
void modify_Goods(MYSQL *);
// void inquiry_G_buying_price(char *);//进价就不弄了
// void modify_discount(float);
protected:
// float G_buying_price;
};


class Root :public Manage{
public:
void add_Manage(MYSQL*);
void del_Manage(MYSQL*);
void inquiry_total(MYSQL*);
void inquiry_user(MYSQL*);
};
bool is_number(string str);

//fuction.h头文件

#include "user.h"


void ROOT(MYSQL*);
void MANAGE(MYSQL*);
void DOMESTIC(MYSQL*);

//user.cpp代码

#include "user.h"


Goods  *goods;
float sum = 0;
/********************************普通用户**********************************/
/*初始化*/
Domestic::Domestic()//到底需要不？？
{
goods = (Goods *)malloc(sizeof(Goods));
goods->G_ID = (char *)malloc(20);
goods->G_name = (char *)malloc(100);
goods->G_amount = (char *)malloc(20);
goods->discount = (char *)malloc(20);
goods->G_selling_price = (char *)malloc(20);
goods->manufacture = (char *)malloc(100);


memset(goods->G_ID, 0, 20);
memset(goods->G_name, 0, 100);
memset(goods->G_amount, 0, 20);
memset(goods->discount, 0, 20);
memset(goods->G_selling_price, 0, 20);
memset(goods->manufacture, 0, 100);





// goods->discount = "1";
}


/*析构函数*//*析构函数这块会有中断，有错误
Domestic::~Domestic()
{
free(goods->manufacture);
free(goods->G_selling_price);
free(goods->discount);
free(goods->G_amount);
free(goods->G_name);
free(goods->G_ID);
free(goods);
}*/


/*输入查找的ID或商品名*/
char * Domestic::putin(MYSQL* mysql)
{
char* str;
str = (char *)malloc(5);
memset(str, 0, 5);
int j = 0;
int result = 0;
cout << "输入商品信息：\n";
cin >> str;
if (is_number(str))
{
goods->G_ID = str;
result = 1;
// return 1;//1 表示输入数据为 ID
}
else
{
goods->G_name = str;
// return 0;//0表示输入为 名字
}
return find(mysql, result);
}


/*查找对应的商品并打印其信息*/
char * Domestic::find(MYSQL* mysql,int f)//f表示查找输入的是ID 还是名字
{
MYSQL_RES *res;


MYSQL_ROW row;
row = (MYSQL_ROW)malloc(sizeof(MYSQL_ROW));
memset(row, 0, sizeof(MYSQL_ROW));


char *buff;
buff = (char *)malloc(500);
memset(buff, 0, 500);


strcat_s(buff, sizeof("select G_ID,G_name,G_amount,G_selling_price,manufacture,discount from Goods where "), "select ID,Name,Amount,Selling_price,Manufacture,Discount from Goods where ");

if (f == 1)
{
strcat_s(buff, 100 + sizeof(buff) + sizeof("G_ID = "), "ID = ");//中间其实是合并后的大小
strcat_s(buff, 100 + sizeof(buff)+sizeof(goods->G_ID), goods->G_ID); 
mysql_query(mysql, buff);


res = mysql_store_result(mysql);
row = mysql_fetch_row(res);


if (row == 0)
cout << "没有此商品！" << endl;
else
cout << "货物编号：" << *row << endl << "货物名称：" << *(row + 1) << endl << "货物存货：" << *(row + 2) << endl << "货物单价：" << *(row + 3) << endl << "货物厂家：" << *(row + 4) << endl << "货物折扣：" << *(row + 5) << endl;
}
if (f == 0)
{
strcat_s(buff, sizeof("G_name = Goods->G_name"), "G_name = Goods->G_name");
mysql_query(mysql, buff);


res = mysql_store_result(mysql);
row = mysql_fetch_row(res);
if (row == 0)
cout << "没有此商品！" << endl;
else
cout << "货物编号：" << *row << endl << "货物名称：" << *(row + 1) << endl << "货物存货：" << *(row + 2) << endl << "货物单价：" << *(row + 3) << endl << "货物厂家：" << *(row + 4) << endl << "货物折扣：" << *(row + 5) << endl;
}
free(buff);
return *(row + 3);
}


/*输入购买的数量*/
void Domestic::inumber(MYSQL* mysql)
{
float i = 0;


char* p = putin(mysql);
float f = strtof(p, NULL);
cout << "输入购买数量！" << endl;
cin >> i;
sum = sum + i * f;
cout << "需要缴付的金额为：" << i * f << endl;
}


/*判断是否为数字*/
bool is_number(string str)
{
if (str.c_str()[0] != 45)
{
for (int i = 0; i < str.length(); i++)
{
if (str.c_str()[i] < '0' || str.c_str()[i] > '9')
{
return false;
}
}
return true;
}
else
{
for (int i = 1; i < str.length(); i++)
{
if (str.c_str()[i] < '0' || str.c_str()[i] > '9')
{
return false;
}
}
return true;
}
}


/*********************************管理用户************************************/
/*添加普通用户*/
void Manage::add_Domestic(MYSQL* mysql)
{

char *name;
name = (char *)malloc(50);
memset(name, 0, 100);


char* key;
key = (char *)malloc(10);
memset(key, 0, 10);


char* id;
id = (char *)malloc(10);
memset(id, 0, 10);


char *buff;
buff = (char *)malloc(200);
memset(buff, 0, 100);


cout << endl << "输入ID号：";
cin >> id;
cout << endl << "输入姓名：";
cin >> name;
cout << endl << "输入密码：";
cin >> key;


strcat_s(buff, 10 + sizeof("insert into users values("), "insert into users values(");
strcat_s(buff, 20 + sizeof(buff) + sizeof(id), id);
strcat_s(buff, 30 + sizeof(buff)+sizeof(char), ",'");
strcat_s(buff, 40 + sizeof(buff) + sizeof(name), name);
strcat_s(buff, 50 + sizeof(buff)+sizeof(char), "',");
strcat_s(buff, 60 + sizeof(buff) + sizeof(key), key);
strcat_s(buff, 70 + sizeof(buff)+sizeof(")"), ")");


mysql_query(mysql, buff);//mysql写入和读取数据这块不懂


// free(name);
// free(buff);
// free(id);
// free(key);
}


/*删除普通用户*/
void Manage::del_Domestic(MYSQL* mysql)
{
char* id;
id = (char *)malloc(10);
memset(id, 0, 10);


cout << endl << "输入ID号：";
cin >> id;

char *buff;
buff = (char *)malloc(100);
memset(buff, 0, 100);


strcat_s(buff, sizeof("delete from users where ID = "), "delete from users where ID = ");
strcat_s(buff, 20 + sizeof(buff) + sizeof(id), id);


mysql_query(mysql, buff);


free(buff);
free(id);
}


/*增加货物*/
void Manage::add_Goods(MYSQL *mysql)
{

cout << endl << "商品ID：";
cin >> goods->G_ID;
cout << endl << "商品名字：";
cin >> goods->G_name;
cout << endl << "商品价格：";
cin >> goods->G_selling_price;
cout << endl << "商品数量：";
cin >> goods->G_amount;
cout << endl << "商品折扣：";
cin >> goods->discount;
cout << endl << "商品厂商：";
cin >> goods->manufacture;



char *buff;
buff = (char *)malloc(500);
memset(buff, 0, 500);


strcat_s(buff, sizeof("insert into GOODS values("), "insert into GOODS values(");
strcat_s(buff, 20 + sizeof(buff)+sizeof(goods->G_ID), goods->G_ID);
strcat_s(buff, 20 + sizeof(buff)+sizeof(char), ",'");
strcat_s(buff, 30 + sizeof(buff)+sizeof(goods->G_name), goods->G_name);
strcat_s(buff, 40 + sizeof(buff)+sizeof(char), "',");
strcat_s(buff, 40 + sizeof(buff)+sizeof(goods->G_selling_price), goods->G_selling_price);
strcat_s(buff, 50 + sizeof(buff)+sizeof(char), ",");
strcat_s(buff, 50 + sizeof(buff)+sizeof("goods->G_amount"), goods->G_amount);
strcat_s(buff, 60 + sizeof(buff)+sizeof(char), ",'");
strcat_s(buff, 60 + sizeof(buff)+sizeof("goods->manufacture"), goods->manufacture);
strcat_s(buff, 70 + sizeof(buff)+sizeof(char), "',");
strcat_s(buff, 70 +sizeof(buff)+sizeof("goods->discount"), goods->discount);
strcat_s(buff, 70 + sizeof(buff)+sizeof(")"), ")");


mysql_query(mysql, buff);


free(buff);
}


/*删除货物*/
void Manage::del_Goods(MYSQL *mysql)//到底要不要分配内存 要不要初始化
{
// Goods goods;
cout << endl << "商品ID：";
cin >> goods->G_ID;


char *buff;
buff = (char *)malloc(200);//
memset(buff, 0, 200);

strcat_s(buff, sizeof("delete from GOODS where ID = "), "delete from GOODS where ID = ");
strcat_s(buff, 20 + sizeof(buff)+sizeof(goods->G_ID), goods->G_ID);


mysql_query(mysql, buff);


free(buff);
}


/*修改物品*/
void  Manage::modify_Goods(MYSQL *mysql)
{
// Goods goods;
cout << endl << "商品ID：";
cin >> goods->G_ID;
cout << endl << "商品名字：";
cin >> goods->G_name;
cout << endl << "商品价格：";
cin >> goods->G_selling_price;
cout << endl << "商品数量：";
cin >> goods->G_amount;
cout << endl << "商品厂商：";
cin >> goods->manufacture;
cout << endl << "商品折扣：";
cin >> goods->discount;


char *buff;
buff = (char *)malloc(500);
memset(buff, 0, 500);


strcat_s(buff, sizeof("delete from GOODS where ID = "), "delete from GOODS where ID = ");
strcat_s(buff, 20 + sizeof(buff)+sizeof(goods->G_ID), goods->G_ID);
mysql_query(mysql, buff);
memset(buff, 0, 500);
strcat_s(buff, sizeof("insert into GOODS values("), "insert into GOODS values(");
strcat_s(buff, 20 + sizeof(buff)+sizeof(goods->G_ID), goods->G_ID);
strcat_s(buff, 20 + sizeof(buff)+sizeof(char), ",'");
strcat_s(buff, 30 + sizeof(buff)+sizeof(goods->G_name), goods->G_name);
strcat_s(buff, 30 + sizeof(buff)+sizeof(char), "',");
strcat_s(buff, 30 + sizeof(buff)+sizeof(goods->G_selling_price), goods->G_selling_price);
strcat_s(buff, 30 + sizeof(buff)+sizeof(char), ",");
strcat_s(buff, 30 + sizeof(buff)+sizeof("goods.G_amount"), goods->G_amount);
strcat_s(buff, 30 + sizeof(buff)+sizeof(char), ",'");
strcat_s(buff, 40 + sizeof(buff)+sizeof("goods.manufacture"), goods->manufacture);
strcat_s(buff, 40 + sizeof(buff)+sizeof(char), "',");
strcat_s(buff, 40 + sizeof(buff)+sizeof("goods.discount"), goods->discount);
strcat_s(buff, 40 + sizeof(buff)+sizeof(")"), ")");


mysql_query(mysql, buff);

free(buff);
}


/*********************************ROOT用户************************************/
/*添加管理用户*/
void Root::add_Manage(MYSQL* mysql)
{
char *name;
name = (char *)malloc(50);
memset(name, 0, 100);


char* key;
key = (char *)malloc(10);
memset(key, 0, 10);


char* id;
id = (char *)malloc(10);
memset(id, 0, 10);


char *buff;
buff = (char *)malloc(200);
memset(buff, 0, 100);


cout << endl << "输入ID号：";
cin >> id;
cout << endl << "输入姓名：";
cin >> name;
cout << endl << "输入密码：";
cin >> key;


strcat_s(buff, 10 + sizeof("insert into users values("), "insert into users values(");
strcat_s(buff, 20 + sizeof(buff)+sizeof(id), id);
strcat_s(buff, 30 + sizeof(buff)+ sizeof(char), ",'");//为什么总是你不对，这一块的值到底是多少？
strcat_s(buff, 40 + sizeof(buff)+sizeof(name), name);
strcat_s(buff, 50 + sizeof(buff)+sizeof(char), "',");
strcat_s(buff, 60 + sizeof(buff)+sizeof(key), key);
strcat_s(buff, 70 + sizeof(buff)+sizeof(char), ")");
strcat_s(buff, 80 + sizeof(buff)+sizeof(char), ";");


mysql_query(mysql, buff);//mysql写入和读取数据这块不懂


// free(name);
// free(buff);
// free(id);
// free(key);
}


/*删除管理用户*/
void Root::del_Manage(MYSQL* mysql)
{
char* id;
id = (char *)malloc(10);
memset(id, 0, 10);


cout << endl << "输入ID号：";
cin >> id;


char *buff;
buff = (char *)malloc(100);
memset(buff, 0, 100);


strcat_s(buff, sizeof("delete from users where ID = "), "delete from users where ID = ");
strcat_s(buff, 20 + sizeof(buff)+sizeof(id), id);


mysql_query(mysql, buff);


free(buff);
free(id);
}


/*收入总和*/
void Root::inquiry_total(MYSQL* mysql)
{
cout <<"今日营业额为："<< sum << endl;
}


/*收入总和*/
void Root::inquiry_user(MYSQL* mysql)
{
MYSQL_RES *res;
MYSQL_ROW row;
row = (MYSQL_ROW)malloc(sizeof(MYSQL_ROW));
memset(row, 0, sizeof(MYSQL_ROW));


mysql_query(mysql, "select * from users");
res = mysql_store_result(mysql);
// row = mysql_fetch_row(res);
//下面的这个while语句 不知道能偶行得通
while (row = mysql_fetch_row(res))//一次读一行
{
for (int t = 0; t < (int)mysql_num_fields(res); t++)
{
printf("%16s  ", row[t]);
}
printf("\n");
}
}

//fuction.cpp文件

#ifndef _FUCTION_H
#define _FUCTION_H
#include "fuction.h"
//root 用户的操作部分
int quit = 0;//用来 确定是否退出当前循环，0表示不退出，1表示退出
Root root;
Manage manage;
Domestic domestic;
void func(int u, MYSQL* mysql)
{
switch (u)
{
case 1:
ROOT(mysql);
break;
case 2:
MANAGE(mysql);
break;
case 3:
DOMESTIC(mysql);
break;
}
}


void ROOT(MYSQL* mysql)
{
int choice = 0;
while (!quit)
{
cout << "请选择如下所需的操作：" << endl;
cout << "0、退出root用户操作。" << endl;
cout << "1、添加管理用户。" << endl;
cout << "2、删除管理用户。" << endl;
cout << "3、收额查询。" << endl;
cout << "4、用户查询。" << endl;


cin >> choice;


switch (choice)
{
case 1:root.add_Manage(mysql); break;
case 2:root.del_Manage(mysql); break;
case 3:root.inquiry_total(mysql); break;
case 4:root.inquiry_user(mysql); break;
case 0:quit = 1; break;
default:cout << "输入有误，请重新输入！" << endl; break;
}
}
quit = 0;
}


//manage用户的操作部分
void MANAGE(MYSQL* mysql)
{
int choice = 0;
while (!quit)
{
cout << "请选择如下所需的操作：" << endl;
cout << "0、退出manage用户操作。" << endl;
cout << "1、添加普通用户。" << endl;
cout << "2、删除普通用户。" << endl;
cout << "3、添加商品。" << endl;
cout << "4、删除商品。" << endl;
cout << "5、修改商品。" << endl;

cin >> choice;


switch (choice)
{
case 1:manage.add_Domestic(mysql); break;
case 2:manage.del_Domestic(mysql); break;
case 3:manage.add_Goods(mysql); break;
case 4:manage.del_Goods(mysql); break;
case 5:manage.modify_Goods(mysql); break;
case 0:quit = 1; break;
default:cout << "输入有误，请重新输入！" << endl; break;
}
}
quit = 0;
}


//domestic用户的操作部分
void DOMESTIC(MYSQL* mysql)
{
int choice = 0;
while (!quit)
{
cout << "请选择如下所需的操作：" << endl;
cout << "0、退出domestic用户操作。" << endl;
cout << "1、查找商品。" << endl;
cout << "2、购买商品。" << endl;


cin >> choice;


switch (choice)
{
case 1:domestic.putin(mysql); break;//完成查找功能
case 2:domestic.inumber(mysql); break;//完成购买功能
case 0:quit = 1; break;
default:cout << "输入有误，请重新输入！" << endl; break;
}
}
quit = 0;
}


#endif

//源.cpp文件

#include "winsock.h"
#include "fuction.h"
using namespace std;
#define MAX 512


MYSQL * mysql;
char* Code;//用户密码
char* Name;
int whitch = 0;


//创建数据库，用户表、商品表
void createdb()
{
mysql = (MYSQL *)malloc(sizeof(MYSQL));
mysql_init(mysql);
mysql_real_connect(mysql, "localhost", "root", "666666", 0, 3306, NULL, 0);
mysql_query(mysql, "create database caigaojian");
mysql_select_db(mysql, "caigaojian");
mysql_query(mysql, "create table GOODS(ID int(4) not null primary key auto_increment,Name varchar(20) not null,Amount int,Selling_price float,Manufacture char(30),Discount float)");
mysql_query(mysql, "create table users(ID int(4) not null primary key auto_increment,Name varchar(20) not null,code int)");
mysql_query(mysql, "insert into users value(1,'root',1)");
}


//比较存储的密码、输入的密码是否相等
int compare(char *codec, char *codes)
{
return strcmp(codec, codes);
}


//匹配用户是哪一个
int marry()
{
int result = 0;
MYSQL_RES *res;
MYSQL_ROW row;
row = (MYSQL_ROW)malloc(sizeof(MYSQL_ROW));
memset(row, 0, sizeof(MYSQL_ROW));

res = mysql_store_result(mysql);
row = mysql_fetch_row(res);
/* while (row = mysql_fetch_row(res))
{
for (int t = 0; t < mysql_num_fields(res); t++)
{
printf("!%s!", row[t]);
}
printf(".............\n");
}
cin >> Name;
*/
if (row == 0)
cout << "用户名错误" << endl;



else if (compare(*row, Code) == 0)
{
cout <<"当前用户是："<< *(row+1) << endl;
result = 1;
}
else
cout << "密码错误！" << endl;
return result;
}


//根据编号取回密码,和用户名
void get_code(char *ID)
{
char* buffer;//用来 传递 数据库 指令的
buffer = (char *)malloc(MAX);
memset(buffer, 0, MAX);


strcat_s(buffer, sizeof("select code,name from users where ID = "), "select code,name from users where ID = ");//指令
strcat_s(buffer, MAX, ID);
mysql_query(mysql, buffer);
// free(buffer);
}


//用户输入
char* putin()
{
char* Id;//获取输入的用户编号

Id = (char *)malloc(100);
Code = (char *)malloc(100);
Name = (char *)malloc(100);

memset(Id, 0, 100);
memset(Code, 0, 100);
memset(Name, 0, 100);


cout << "输入用户编号：" << endl;
cin >> Id;
cout << "输入用户密码：" << endl;
cin >> Code;


return Id;
}
void func(int u, MYSQL* mysql);


int main()
{
createdb();//创建数据库 和 表
char *c;
int result = 1;
char s;
while (result)
{
c = putin();// 输入编号 和密码
int i = (int)(c[0] - '0');//字符‘3’的ASCII为51
get_code(c);//根据编号取回密码
if (marry())//匹配用户
func(i, mysql);
cout << "是否退出？（Y/N）" << endl;
cin >> s;
if (s == 'Y')
result = 0;
}
mysql_close(mysql);
// system("pause");
return 0;
}

以上为全部代码，能够执行所有功能。代码很简单，初学mysql者用。

注：使用时，将 源.cpp中的 mysql_real_connect(mysql, "localhost", "root", "666666", 0, 3306, NULL, 0);中“666666”改为你自己的mysql密码即可。

我所遇问题的归纳。

1、在运行后，按F5会出现上一次从键盘输入的内容。如linux中的history的（↑）。

2、strcat_s(x,x,x); 

这个函数在使用时一直出现中断。因为我用了很多这个函数，所有后一个我直接加了很大的数据长度，代码中很容易找到。

3、在row = mysql_fetch_row(res);中

通过vs单步执行时，分析row、res其结构数据时，有很多不明白。

4、在每次定义一个char *buff;时，分配内存、初始化、初始化的大小，得注意。否则易出现中断。

5、代码中出现了一次goods->discount处的中断，这个值只是用来接收外部输入的，即键盘输入。

问题在于我分配内存并memset后，再给他赋了一个值‘1’。这就是原因，至于为什么，还未研究。

这博客第一是给我自己记录用的，然后才是供大家参考，所以我会记录一些我自己要解决的问题，自己不足的地方。读者可以略过！！

我自己欠缺的地方

1. goods 到底是用结构体还是用类？

2.类的构造函数要不要自己定义、还是直接用默认的？

3.构造函数怎么写，写几个，内容写什么？

4.析构函数怎么写，些什么?free内存分配到底是在析构中写，还是在变量用完之后？

5.在写了多个头文件后，反复包含会出现重复定义。那怎么写、规范是什么？

此代码时间  2015.12.2 开始-- 2015.12.5完成。