c++连接MySql进阶

c++ 写MySql工具类

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本文主要总结和记录又本人设计的一个mysql连接工具类SqlPackage。
本工具类提供了常用的sql命令的执行接口，利用本工具类提供的方法能够非常地方便地
在c++代码中实现绝大部分的常用数据库操作。
以下链接是一个使用本工具实现的 学生成绩管理系统案例：
BlackCarDriver/student-manage-system
若初次在c++中使用mysql数据库连接可以参考我的上一篇博客：
c++连接mysql入门

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sqlPackage.h

#include<iostream>
#include<string>
#include<vector>
using namespace std;

typedef vector<string> res_row;

class SqlPackage {
private:
	static MYSQL conn;
	static bool isInit;
	MYSQL_RES	*res_set;
	MYSQL_ROW	row;
	MYSQL_FIELD *field;
	int init();
	string query(string ope, int interval);
	string getTableHead(MYSQL_RES* res, int interval);
public:
	SqlPackage();
	~SqlPackage();
	void testQuery();
	void testExec();
	void testOther();
	res_row queryRow(string ope);
	int exec(string ope);
	string makeSql(string format, vector<string> strVec);
	int insert(string insertSql);
	int login(string id, string password);
	void printTable(string ope, int interval=20);
};

sqlPackage.cpp

#pragma once
#include<iostream>
#include<stdio.h>
#include<string>
#include<string.h>
#include<winsock.h>
#include<mysql.h>
#include<vector>
#include"SqlPackage.h"
using namespace std;

#define SCUUEED 1
#define FATAL	-1
#define	WORNG	-2
#define TEACHER 3
#define	STUDENT	9
#define MANAGER	27

//config of database connection
const char* host = "localhost";
const char* user = "root";
const char* password = "123456";
const char* database = "school";
const  int port = 3306;

//static mumber
MYSQL SqlPackage::conn;
bool SqlPackage::isInit = false;

SqlPackage::SqlPackage(){
	int res = init();	//init will return false when connect fall
	if (res == FATAL){
		exit(1);
	} 
}

SqlPackage::~SqlPackage(){
	mysql_close(&conn);
}

int SqlPackage::init(){
	if (isInit){
		return SCUUEED;
	}
	else {
		isInit = true;
	}
	mysql_init(&conn);
	bool is_scueed = mysql_real_connect(&conn, host, user, password, database, port, NULL, 0);
	if (!is_scueed){
		fprintf(stderr, "Failed to connect to database: Error: %s\n", mysql_error(&conn));
		return	FATAL;
	}
	mysql_query(&conn, "SET NAMES utf8");
	printf("Connect database scuueed! \n");
	return	SCUUEED;
}

// the funtion name with test*() mainly purpose on testing the work of it package function. 
void SqlPackage::testQuery(){
	string queryStr = "select * from t_account";
	string result = query(queryStr, 15);
	cout << result << endl;
}

void SqlPackage::testExec(){
	string insertStr = "INSERT INTO t_account(id,NAME,TYPE)VALUES('1234571','test2','manager');";
	string deleteStr = "delete from t_account where name ='test2'";
	string updateStr = "UPDATE t_account SET NAME = 'test2' WHERE id = '1234570'";
	int res = exec(updateStr);
	if (res == SCUUEED){
		puts("scuueed!");
	}
	else{
		puts("Fall!");
	}
}

void SqlPackage::testOther(){

}

//query() use to exec a select sql and it will return a string to describe the table you are query.
//you can use interval to set the distant between two column
string SqlPackage::query(string queryStr, int interval){
	int status = mysql_query(&conn, queryStr.c_str());
	if (status != 0){
		return "query error ... \n";
	}
	res_set = mysql_store_result(&conn);
	int count = mysql_num_rows(res_set);
	if (count <= 0){
		return "no result ... \n";
	}
	string result = "";
	result += getTableHead(res_set, interval);
	int colNum = mysql_num_fields(res_set);
	while ((row = mysql_fetch_row(res_set)) != NULL){
		for (int i = 0; i< colNum; i++){
			string tmp = (row[i] != NULL ? row[i] : "NULL");
			tmp.resize(interval, ' ');
			result += tmp;
		}
		result += "\n";
	}
	mysql_free_result(res_set);
	return result;
}

//queryRow() user to exec some sql that only return a row of result, such as select count(*)
res_row SqlPackage::queryRow(string queryStr){
	res_row result;
	int status = mysql_query(&conn, queryStr.c_str());
	if (status != 0) {
		cout << "query row error ... \n";
		return result;
	}
	res_set = mysql_store_result(&conn);
	int count = mysql_num_rows(res_set);
	if (count == 0){
		cout << "no result ... ";
		return result;
	}
	row = mysql_fetch_row(res_set);
	for (int i = 0; i< mysql_num_fields(res_set); i++){
		string tmp = (row[i] != NULL ? row[i] : "NULL");
		result.push_back(tmp);
	}
	return result;
}

//getTableHead return the name of columns, it is a private function used by query()
string SqlPackage::getTableHead(MYSQL_RES* res, int interval){
	string tableHead = "";
	int colNum = mysql_num_fields(res);
	MYSQL_FIELD* field = mysql_fetch_fields(res);
	for (int i = 0; i < colNum; i++){
		string colName = field[i].name;
		colName.resize(interval, ' ');
		tableHead += colName;
	}
	tableHead += "\n";
	string tmp = "-";
	tmp.resize(interval*colNum, '-');
	tableHead += tmp;
	tableHead += "\n";
	return tableHead;
}

//exec() mainly execu some sql command that just return scuueed or fatal. 
//you can use it to execu insert, delete update command and so on..
int SqlPackage::exec(string ope){
	if (mysql_query(&conn, ope.c_str())){
		return FATAL;
	}
	return SCUUEED;
}

//it function used by main(), you can identify user type by the return result
int SqlPackage::login(string id, string password){
	int result = WORNG;
	string loginTemplace = "select type from t_account where id = '$1' and password = '$2'";
	string loginSql = makeSql(loginTemplace, { id, password });
	res_row res = queryRow(loginSql);
	if (res.size() >0){
		cout << res[0] << endl;
		if (res[0] == "teacher") result = TEACHER;
		if (res[0] == "student") result = STUDENT;
		if (res[0] == "manager") result = MANAGER;
	}
	else{
		puts("Password worng or account not exist...");
		result = WORNG;
	}
	return result;
}

//it is a userful function, format is the template of a sql, strVec is the container of args
string SqlPackage::makeSql(string format, vector<string> strVec){
	string result = format;
	for (int i = 0; i < strVec.size(); i++){
		string target = "$" + to_string(i + 1);
		auto p = result.find(target);
		result = result.replace(p, 2, strVec[i]);
	}
	return result;
};

//printTable is used to execute some selete command that you are sure it will not go worng
void SqlPackage::printTable(string ope, int interval){
	string table = query(ope, interval);
	cout << table;
}

int SqlPackage::insert(string insertSql){
	int result = exec(insertSql);
	return result;
}