The use of common APIs for database_

Database_API

Continuing from the database in the previous article, and then do some simple analysis on the functions of the database.
The reference link of this article:
MySQL C API usage (basic functions)
Mysql C API function detailed explanation

Common APIs of MySQL

When a commonly used program calls the MySQL database, it usually calls the following APIs, which will be analyzed one by one below.

mysql_init()
```
//函数原型
MYSQL *STDCALL mysql_init(MYSQL *mysql);
```
This APIis mainly used to allocate or initialize an MySQLobject to connect to the MySQL server;
the return value is MYSQL *;
the parameter MYSQL *mysqlis to specify an MYSQLobject.
mysql_options()
```
//函数原型
int STDCALL mysql_options(MYSQL *mysql, enum mysql_option option,
                      const void *arg);
```
This APIcan be used to set additional connection options and affect the behavior of the connection. This function can be called multiple times to set several options; the
parameter MYSQL *mysqlis to specify an MYSQLobject;
the parameter enum mysql_option optionis the connection option for the caller to choose to fill in;
the parameter const void *argis combined with the previous parameter The value of the connection option to fill in.

For filling in the connection options, you can refer to the mysql_options() function
mysql_real_connect()
```
//函数原型
MYSQL *STDCALL mysql_real_connect(MYSQL *mysql, const char *host,
                                  const char *user, const char *passwd,
                                  const char *db, unsigned int port,
                                  const char *unix_socket,
                                  unsigned long clientflag);
```
This APIis mainly used to allocate or initialize an MySQLobject to connect to MySQLthe server.
The parameter MYSQL *mysqlis to specify an MYSQLobject, here is mysql_initthe pointer returned by the function;
the parameter const char *hostspecifies the host address;
the parameter const char *userspecifies mysqlthe user name;
the parameter const char *passwdenters the password of the user name;
the parameter const char *dbSpecify the database, and link to the default database when the value is empty;
the parameter unsigned int portspecifies the port;
the parameter const char *unix_socketspecifies the use of unix link mode, and when it is empty, it indicates that it is not applicable socketor the pipeline mechanism;
the parameter unsigned long clientflagis usually set to 0.
mysql_query()
```
//函数原型
int STDCALL mysql_query(MYSQL *mysql, const char *q);
```
This APIis the most commonly used, and it is used in adding, deleting, checking, and modifying. queryIt means query in English, but it means here 执行.
The parameter MYSQL *mysqlis to specify an MYSQLobject.
The parameter const char *enters a SQLstatement.
mysql_store_result()
```
//函数原型
MYSQL_RES *STDCALL mysql_store_result(MYSQL *mysql);
```
Obtaining the result set is usually used with mysql_querythis APIto query SQLthe result returned by the previous statement.
The parameter MYSQL *mysqlis to specify an MYSQLobject
and the return value MYSQL_RESis a handle, which can be used to mysql_fetch_rowretrieve how many rows of data there are in the result set.
mysql_use_result()
```
//函数原型
MYSQL_RES *STDCALL mysql_use_result(MYSQL *mysql);
```
This APIis to use this function to obtain the result set after calling a command that can generate a result set; the
parameter MYSQL *mysqlis to specify an MYSQLobject.
mysql_fetch_row()
```
//函数原型
MYSQL_ROW STDCALL mysql_fetch_row(MYSQL_RES *result);
```
Used in conjunction with mysql_store_resultthis APIto get the content of each row.
The parameter MYSQL_RES *resultis mysql_use_resultthe return value obtained through the get.
mysql_free_result()
```
//函数原型
void STDCALL mysql_free_result(MYSQL_RES *result);
```
After operating the result set, be sure to call this function to release the memory;
the parameter MYSQL_RES *resultis mysql_use_resultthe return value obtained through.
mysql_error()
```
//函数原型
const char *STDCALL mysql_error(MYSQL *mysql);
```
The return value of the function is const char*the type, mainly to return mysqlwhat error information occurred when the function was called recently.
The parameter MYSQL *mysqlis to specify an MYSQLobject
mysql_close()
```
//函数原型
void STDCALL mysql_close(MYSQL *sock);
```
mysql_close()Every program that calls the database connection must be called in the final stage.
Obviously, its function is to close the connection of a MySQL server.
The parameter MYSQL *mysqlis to specify an MYSQLobject

MySQL API application

Let's use a more practical example to APIwrite a simple stand-alone database management software.
Create two tables in the local database and store some initial information:
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First define the include file:
define.h

#pragma once
#define _CRT_SECURE_NO_WARNINGS
#include <mysql.h>
#include <iostream>
#include <iomanip>
#include <string>
#include <sstream>
#include <assert.h>
#pragma comment(lib,"libmysql.lib")

Define a management class:CManager

Provides the display of the main menu, the functions of connecting to the database and printing errors.

CManager.h

#pragma once
#include "define.h"
#include "CWorker.h"
#include "CAdmin.h"
class CManager
{
	MYSQL m_sql;
	CWorker m_work;
	CAdmin m_admin;
	int Menu();
	bool ConnectDB();
public:
	int Main();
	static void PrintError(std::string sPromp)
	{
		auto & sql = getInstance().m_sql;
		std::cout << sPromp << "(" << mysql_errno(&sql) << "):" 
			<< mysql_error(&sql) << std::endl;
		system("pause");
	}
	static CManager& getInstance()
	{
		static CManager m;
		return m;
	}
	CManager() : m_admin(m_sql),m_work(m_sql)
	{

	}
};

CManager.cpp

#include "CManager.h"
using namespace std;
int CManager::Menu()
{
	system("cls");

	const char* sPrior = m_admin.GetPrior() ? "普通" : "高级";
	cout << "\n\n\t\t当前用户：" << m_admin.GetUser() << "【" << sPrior << "】" << endl;
	puts("\t\t********************************");
	puts("\t\t*\t1、浏览所有信息        *");
	puts("\t\t*\t2、添加信息            *");
	puts("\t\t*\t3、删除信息            *");
	puts("\t\t*\t4、修改信息            *");
	puts("\t\t*\t5、查找信息            *");
	if (m_admin.GetPrior())
		puts("\t\t*\t6、密码修改            *");
	else
		puts("\t\t*\t6、管理账号            *");

	puts("\t\t*\t0、退出                *");
	puts("\t\t********************************");
	cout << "\t\t请选择：";
	int i = 0;
	cin >> i;

	switch (i)
	{
	case 1:
		m_work.Browse();
		//m_work.Print();
		break;
	case 2:
		m_work.Input();
		break;
	case 3:
		m_work.Delete();
		break;
	case 4:
		m_work.Modify();
		break;
	case 5:
		m_work.Find();
		break;
	case 6:
		m_admin.Main();
	}
	return i;
}

bool CManager::ConnectDB()
{
	if (!mysql_init(&m_sql))
	{
		cout << "数据库初始化失败："  << mysql_error(&m_sql) << endl;
		return false;
	}

	if (!mysql_real_connect(&m_sql, "localhost", "root", "123456", "worker", 3306, nullptr, 0))
	{
		cout << "连接数据库失败(" << mysql_errno(&m_sql) << "):" << mysql_error(&m_sql) << endl;
		return false;
	}
	mysql_query(&m_sql, "set names \'GBK\'");
    return true;
}

int CManager::Main()
{
    if (!ConnectDB())
        return -1;
	if (!m_admin.Login())
		return -1;
    while (Menu())
        ;
    return 0;
}

For the singleton mode of C++, please refer to Learning: Singleton mode in C++

Define another account management class:CAdmin

Functions mainly include account management options, account addition, deletion, modification and query operations.

CAdmin.h

#pragma once
#include "define.h"

class CAdmin
{
	MYSQL &m_sql;
	int m_nPrior{0};
	std::string m_sName, m_sPass;
	MYSQL_ROW FindName(const char* sName);
	bool Check(const char* sName, const char* sPass);
	void PrintRow(MYSQL_ROW row);
	void Print()
	{
		Select("SELECT *FROM t_admin");
	}
	void InsertData(const std::string& sName, const std::string& sPass, int nPrior);
	void DeleteData(const std::string& sName);
	void Input();
	void Delete();
	void ChangePass();
	void ChangePass(std::string sNew);
	int Menu();
	void Select(const char* sSQL);
public:
	int Main();
	bool Login();

	CAdmin(MYSQL &sql) :m_sql(sql)
	{

	}
	int GetPrior() const
	{
		return m_nPrior;
	}
	const char* GetUser() const
	{
		return m_sName.c_str();
	}
};

CAdmin.cpp

#include "CAdmin.h"
#include "CManager.h"
using namespace std;

MYSQL_ROW CAdmin::FindName(const char* sName)
{
    stringstream ss;
    ss << "SELECT * FROM t_admin WHERE f_name = '" << sName <<"'";

    int n = mysql_query(&m_sql, ss.str().c_str());
    if (n)
    {
        CManager::PrintError("查找账号时发生错误"+ ss.str());
        return nullptr;
    }
    auto res = mysql_store_result(&m_sql);
    if (!res)
        return nullptr;
    return mysql_fetch_row(res);
}
bool CAdmin::Check(const char* sName, const char* sPass)
{
    string sSQL =  "SELECT* FROM t_admin WHERE f_name = '";
    sSQL += sName;
    sSQL += "' AND binary f_pass = '";
    sSQL += sPass;
    sSQL += "'";

    int n = mysql_query(&m_sql, sSQL.c_str());
    if (n)
    {
        cout << "登录失败，数据库查询错误：" << mysql_error(&m_sql);
        return false;
    }

    auto res = mysql_store_result(&m_sql);
    if (res && mysql_num_rows(res) > 0)
    {
        auto row = mysql_fetch_row(res);
        m_sName =*row++;
        m_sPass = *row++;
        m_nPrior = atoi(*row);
        return true;
    }

    cout << "你输入的账号或密码错误！" << endl;
    return false;
}

void CAdmin::PrintRow(MYSQL_ROW row)
{
    assert(row);
    const char* str = *row++;
    if (!str)
        str = "无";
    cout << str << '\t';
    str = *row++;
    if (!str)
        str = "无";
    cout << str << '\t';
    str = *row++;
    if (str)
        str = atoi(str) ? "普通" : "高级";
    else
        str = "无";
    
    cout <<str<< endl;
}

void CAdmin::Select(const char* sSQL)
{
    int n = mysql_query(&m_sql, sSQL);
    if (n)
    {
        CManager::PrintError("打印数据时发生错误：" + string(sSQL));
        return;
    }
    auto res = mysql_store_result(&m_sql);
    if (!res)
    {
        CManager::PrintError("打印数据时获取结果集错误：" + string(sSQL));
        return;
    }
    system("cls");
    const int ws[] = { 6,16,12,0 };
    int i = -1;
    cout <<"账号"<<'\t'<<"密码" <<'\t'<<"权限" << endl;
    //puts("工号\t姓名\t工资\t入职日期");
    MYSQL_ROW row;
    int nCol = mysql_num_fields(res);
    while (row = mysql_fetch_row(res))
        PrintRow(row);

    cout << "总共有 " << mysql_num_rows(res) << " 条记录" << endl;
    system("pause");
}

void CAdmin::InsertData(const std::string& sName, const std::string& sPass, int nPrior)
{
    char sSQL[256];
    sprintf(sSQL, "INSERT INTO t_admin VALUES('%s','%s',%d)", sName.c_str(),
        sPass.c_str(), nPrior);
    if (mysql_query(&m_sql, sSQL))
        CManager::PrintError("插入账号信息时出错");
    else
        Print();
}

void CAdmin::DeleteData(const std::string& sName)
{
    stringstream ss;
    ss << "DELETE FROM t_admin WHERE f_name='" << sName << "'";

    if (mysql_query(&m_sql, ss.str().c_str()))
        CManager::PrintError("删除账号信息时出错"+ss.str());
    else
        Print();
}

void CAdmin::Input()
{
    string sName,sPass;
    int nPrior;
    cout << "请输入新的账号：";
    cin >> sName;
    auto row = FindName(sName.c_str());
    if (row)
    {
        cout << "你输入的账号已存在：";
        PrintRow(row);
        system("pause");
        return;
    }
    cout << "请输入密码和权限（0、高级 1、普通）：";
    cin >>sPass >> nPrior;
    InsertData(sName, sPass, nPrior);
}

void CAdmin::Delete()
{
    string sName, sPass;
    int nPrior;
    cout << "请输入要删除的账号：";
    cin >> sName;
    auto row = FindName(sName.c_str());
    if (!row)
    {
        puts("你输入的账号不存在！");
        system("pause");
        return;
    }

    PrintRow(row);
    printf("你确定要删除这条记录吗？[y/n]");
    char c;
    cin >> c;
    DeleteData(sName);
}
void CAdmin::ChangePass()
{
    string sOld, sNew, sConf;//confirm
    cout << "请输入旧密码：";
    cin >> sOld;
    if (sOld != m_sPass)
    {
        cout << "你输入的旧密码不正确！"<<endl;
        system("pause");
        return;
    }
    cout << "请输入新密码：";
    cin >> sNew;
    cout << "请再次输入新密码：";
    cin >> sConf;
    if (sNew != sConf)
    {
        cout << "两次输入的新密码不一致！" << endl;
        system("pause");
        return;
    }
    if (sNew == m_sPass)
    {
        cout << "新密码和旧密码不能相同！" << endl;
        system("pause");
        return;
    }
    ChangePass(sNew);
}
void CAdmin::ChangePass(std::string sNew)
{
    char sSQL[256];
    sprintf(sSQL, "UPDATE t_admin SET f_pass='%s' WHERE f_name='%s'", sNew.c_str(),
        m_sName.c_str());
    int n = mysql_query(&m_sql, sSQL);
    if (n)
    {
        CManager::PrintError("修改密码时出错！"+string(sSQL));
        return;
    }
    size_t nRows = mysql_affected_rows(&m_sql);
    if (nRows > 0)
    {
        m_sPass = sNew;
        cout << "修改密码成功,总共更新了" << nRows << "条记录" << endl;
    }
    else
        cout << "修改密码失败！" << endl;
    system("pause");
}
int CAdmin::Menu()
{
    system("cls");
    puts("\t\t********************************");
    puts("\t\t*\t1、浏览账号            *");
    puts("\t\t*\t2、添加账号            *");
    puts("\t\t*\t3、删除账号            *");
    puts("\t\t*\t4、修改密码            *");
    puts("\t\t*\t0、返回主菜单           *");
    puts("\t\t********************************");
    cout << "\t\t请选择：";
    int n;
    cin >> n;
    switch (n)
    {
    case 1:
        Print();
        break;
    case 2:
        Input();
        break;
    case 3:
        Delete();
        break;
    case 4:
        ChangePass();
        break;
    }

    return n;
}
int CAdmin::Main()
{
    if (m_nPrior)
        ChangePass();
    else
        while (Menu())
            ;
    return 0;
}
bool CAdmin::Login()
{
    string sName, sPass;
    cout << "请输入账号和密码：" << endl;
    cin >> sName >> sPass;
    return Check(sName.c_str(), sPass.c_str());
}

And define specific work classes:CWorker

Addition, deletion, modification and query of operational data.

CWorker.h

#pragma once
#include "define.h"
#include "CSort.h"
#include "CFind.h"
class CWorker
{
	MYSQL& m_sql;
	CSort m_sort{this};
	CFind m_find{this};
	static void PrintField(MYSQL_ROW row, int nWidth);
	static const int m_ws[] ;
	void ModifyData(int nNumb);
	void Print();

public:
	static void PrintRow(MYSQL_ROW row, int nCol);
	void Find()
	{
		while (m_find.Menu())
			;
	}
	void Browse()
	{
		while (m_sort.Menu())
			;
	}
	void Select(const char* sSQL);
	MYSQL_ROW FindNumb(int nNumb);
	bool DeleteNumb(int nNumb);
	void Delete();
	void Modify();
	void Input();
	CWorker(MYSQL& sql) :m_sql(sql)
	{

	}
};

CWorker.cpp

#include "CWorker.h"
#include "CManager.h"
using namespace std;
const int CWorker::m_ws[] = {6, 16, 12, 0};
//void CWorker::Print()
//{
//	system("cls");
//	int n = mysql_query(&m_sql,"SELECT * FROM t_people");
//	if (n)
//	{
//		CManager::PrintError("打印数据时发生错误：");
//		return;
//	}
//	auto res = mysql_store_result(&m_sql);
//	if (!res)
//	{
//		CManager::PrintError("打印数据时获取结果集错误：");
//		return;
//	}
//	puts("工号\t姓名\t工资\t入职日期");
//	MYSQL_ROW row;
//	int nCol = mysql_num_fields(res);
//	while (row = mysql_fetch_row(res))
//	{
//		n = nCol;
//		while (n--)
//		{
//			auto str = *row++;
//			if (str)
//				cout << str << "\t";
//			else
//				cout << "无\t";
//		}
//		putchar(10);
//	}
//	cout << "总共有 " << mysql_num_rows(res) << " 条记录" << endl;;
//	system("pause");
//}

void CWorker::Print()
{
	Select("SELECT *FROM t_people");
}

void CWorker::PrintField(MYSQL_ROW row, int nWidth)
{
	auto str = *row;
	cout << setiosflags(ios::left) << setw(nWidth);
	if (str)
		cout << str;
	else
		cout << "无";
}

void CWorker::PrintRow(MYSQL_ROW row, int nCol)
{
	int i = -1;
	while (++i < nCol)
		PrintField(row++, m_ws[i]);
	cout << endl;
}


MYSQL_ROW CWorker::FindNumb(int nNumb)
{
	stringstream ss;
	ss << "SELECT * FROM t_people WHERE f_numb = " << nNumb;
	
	int n = mysql_query(&m_sql,ss.str().c_str());
	if (n)
	{
		CManager::PrintError("查找工号时发生错误");
		return nullptr;
	}
	auto res = mysql_store_result(&m_sql);
	if (!res)
		return nullptr;
	return mysql_fetch_row(res);
}
bool CWorker::DeleteNumb(int nNumb)
{
	stringstream ss;
	ss << "DELETE FROM t_people WHERE f_numb = " << nNumb;
	int n = mysql_query(&m_sql, ss.str().c_str());
	if (n)
	{
		CManager::PrintError("删除工号时发生错误");
		return false;
	}
	return true;

}
void CWorker::Delete()
{//size_t n = mysql_affected_rows(&m_sql);
	int nNumb;
	cout << "请输入要删除的工号：";
	cin >> nNumb;
	auto row = FindNumb(nNumb);
	if (!row)
	{
		puts("你输入的工号不存在！");
		system("pause");
		return;
	}

	PrintRow(row, _countof(m_ws));
	printf("你确定要删除这条记录吗？[y/n]");
	char c = 0;

	cin >> c;//不出现类似于getchar 失效问题
	if (c == 'Y' || c == 'y')
	{
		if(DeleteNumb(nNumb))
			Print();
	}
}

void CWorker::ModifyData(int nNumb)
{//size_t n = mysql_affected_rows(&m_sql);
	string sName, sDate;
	float fSala;
	cout << "请输入姓名和工资、入职日期：";
	cin >> sName >> fSala >> sDate;
	char sSQL[256];
	sprintf(sSQL, "UPDATE t_people SET f_name='%s',f_sala=%g,f_date='%s'"
		" WHERE f_numb=%d", sName.c_str(),fSala, sDate.c_str(), nNumb);
	if (mysql_query(&m_sql, sSQL))
		CManager::PrintError("插入员工信息时出错");
	else
		Print();
}
void CWorker::Select(const char* sSQL)
{
	int n = mysql_query(&m_sql, sSQL);
	if (n)
	{
		CManager::PrintError("打印数据时发生错误："+string(sSQL));
		return;
	}
	auto res = mysql_store_result(&m_sql);
	if (!res)
	{
		CManager::PrintError("打印数据时获取结果集错误：" + string(sSQL));
		return;
	}
	system("cls");
	const int ws[] = { 6,16,12,0 };
	int i = -1;
	cout << setiosflags(ios::left) << setw(ws[0]) << "工号" << setw(ws[1])
		<< "姓名" << setw(ws[2]) << "工资" << "入职日期" << endl;
	//puts("工号\t姓名\t工资\t入职日期");
	MYSQL_ROW row;
	int nCol = mysql_num_fields(res);
	while (row = mysql_fetch_row(res))
		PrintRow(row++, nCol);

	cout << "总共有 " << mysql_num_rows(res) << " 条记录" << endl;
	system("pause");
}
void CWorker::Modify()
{
	int nNumb;
	cout << "请输入要修改的工号：";
	cin >> nNumb;
	auto row = FindNumb(nNumb);
	if (!row)
	{
		puts("你输入的工号不存在！");
		system("pause");
		return;
	}
	PrintRow(row, _countof(m_ws));
	printf("你确定要修改这条记录吗？[y/n]");
	char c = 0;
	cin >> c;//不出现类似于getchar 失效问题
	if (c == 'Y' || c == 'y')
		ModifyData(nNumb);
}

void CWorker::Input()
{
	int nNumb;
	cout << "请输入工号：";
	cin >> nNumb;
	auto row = FindNumb(nNumb);
	if (row)
	{
		cout << "你输入的工号已存在：";
		PrintRow(row, _countof(m_ws));
		system("pause");
		return;
	}
	string sName,sDate;
	float fSala;
	cout << "请输入姓名和工资、入职日期：";
	cin >> sName >> fSala>>sDate;
	//stringstream ss;//sprintf
	char sSQL[256];
	sprintf(sSQL,"INSERT INTO t_people VALUES(%d,'%s',%g,'%s')", nNumb, sName.c_str(),
		fSala, sDate.c_str());
	if (mysql_query(&m_sql, sSQL))
		CManager::PrintError("插入员工信息时出错");
	else
		Print();
	//size_t n = mysql_affected_rows(&m_sql);
}

Find class:CFind

Which fields to search for.

CFind.h

#pragma once
#include "define.h"
class CWorker;
class CFind
{
	CWorker* m_pWorker;
	void FindByNumb();
	void FindByName();
	void FindBySalary();
	void FindByDate();
public:
	int Menu();
	CFind(CWorker* pWorker) :m_pWorker(pWorker)
	{
	}
};

CFind.cpp

#include "CFind.h"
#include "CWorker.h"
using namespace std;
void CFind::FindByNumb()
{
	int nNumb;
	printf("请输入要查找的工号：");
	cin >> nNumb;
	auto row = m_pWorker->FindNumb(nNumb);
	if (row)
		m_pWorker->PrintRow(row,4);
	else
		puts("你输入工号不存在！");
	system("pause");
}

void CFind::FindByName()
{
	string sName;//C++字符串
	int nCount = 0;
	cout << "请输入要查找的姓名（模糊查找）：";
	cin >> sName;
	stringstream ss;
	ss << "SELECT *FROM t_people WHERE f_name LIKE '%%" << sName << "%%'";
	m_pWorker->Select(ss.str().c_str());
}

void CFind::FindBySalary()
{
	float fMin, fMax;
	printf("请输入要查的工资段（2个数字）：");
	cin >> fMin >> fMax;
	char sSQL[256];
	sprintf(sSQL, "SELECT * FROM t_people WHERE f_sala>=%g AND f_sala<=%g", fMin, fMax);
	m_pWorker->Select(sSQL);
}

void CFind::FindByDate()
{
	string sMin, sMax;
	printf("请输入要查的日期段(yyyy-mm-dd yyyy-mm-dd)：");
	cin >> sMin >> sMax;
	char sSQL[256];
	sprintf(sSQL, "SELECT * FROM t_people WHERE f_date>='%s' AND f_date<='%s'", 
		sMin.c_str(), sMax.c_str());
	m_pWorker->Select(sSQL);
}

int CFind::Menu()
{
	system("cls");

	puts("\n\n\t\t********************************");
	puts("\t\t*\t1、按工号查找            *");
	puts("\t\t*\t2、按姓名查找            *");
	puts("\t\t*\t3、按工资段查找          *");
	puts("\t\t*\t4、按日期段查找          *");
	puts("\t\t*\t0、返回主查找            *");
	puts("\t\t********************************");
	printf("\t\t请选择：");
	int n;
	scanf_s("%d", &n);
	switch (n)
	{
	case 1:
		FindByNumb();
		break;
	case 2:
		FindByName();
		break;
	case 3:
		FindBySalary();
		break;
	case 4:
		FindByDate();
		break;
	}
	return n;
}

sort class:CSort

CSort.h

#pragma once
class CWorker;
class CSort
{
	CWorker* m_pWorker;
public:
	int Menu();
	CSort(CWorker* pWorker) :m_pWorker(pWorker)
	{

	}
};

CSort.cpp

#include "define.h"
#include "CSort.h"
#include "CWorker.h"
using namespace std;
int CSort::Menu()
{
	system("cls");
	//golang
	puts("\n\n\t\t********************************");
	puts("\t\t*\t1、按工号排序            *");
	puts("\t\t*\t2、按姓名排序            *");
	puts("\t\t*\t3、按工资排序            *");
	puts("\t\t*\t4、按日期排序            *");
	puts("\t\t*\t0、返回主菜单            *");
	puts("\t\t********************************");
	cout <<"\t\t请选择：";
	int n;
	cin >> n;

	if (n > 0 && n < 5)
	{
		string ss[] = { "f_numb","f_name","f_sala","f_date"};
		string sSQL = "SELECT * FROM t_people ORDER BY ";
		sSQL += ss[n - 1];
		m_pWorker->Select(sSQL.c_str());
	}
	return n;
}

Summarize

The above program is mainly the process of designing ideas, and the MYSQLcommonly used ones are called through the program APIto deepen MYSQL APIthe understanding.