database

A modern,fluent simple and cross-platform C++ mysql database library implemented wit C MySQL API.Runtime safety and no exception.

Simple Example

#include <iostream>
#include <iomanip>
#include <string_view>
#include "database/mysql.h"

int main(int argc, char** argv)
{
    std::string user = "user";
    std::string pass = "password";
    std::string host = "127.0.0.1";
    int port = 33123;
    std::string dbname = "user";

    database::MySQL mysql;
    database::Error err = mysql.Connect(user, pass, host, port, dbname);
    if (err) return 1;
    auto query_result = mysql.Query("select `id`,`name`,`rank`,`rate` from `user`.`name`");
    if (err = query_result.Error()) return 1;
    while (database::MySQL::Row row = query_result.Next())
    {
        std::int64_t id = row[0];
        std::string name = row[1];
        int rank = row[2];
        long double rate = row[3];
        std::cout << id << " " << name << " " << rank << " " << rate << std::endl;
    }
    auto execute_result = mysql.Execute(R"(INSERT INTO `user`.`name`(`id`, `name`) VALUES (0, 'user_name');)");
    if (err = execute_result.Error()) return 1;
    std::cout << "affected rows:" << execute_result.AffectedRows() << std::endl;
    return 0;
}

Example With Comment

#include <iostream>
#include <iomanip>
#include <string_view>
#include "database/mysql.h"

int main(int argc, char** argv)
{
    // mysql connection info.
    std::string user = "user";
    std::string pass = "password";
    std::string host = "127.0.0.1";
    int port = 33123;
    std::string dbname = "user";

    // construct MySQL instance without any parameter.
    database::MySQL mysql;

    // err could be cast to bool type.
    // if err == true, error exists while trying to connect to MySQL server.
    database::Error err = mysql.Connect(user, pass, host, port, dbname);
    if (err)
    {
        std::cout << err << std::endl;
        return 1;
    }

    // for select statement,use MySQL::Query.
    // return MySQL::QueryResult
    database::MySQL::QueryResult query_result = mysql.Query(
        "select `id`,`name`,`rank`,`rate` from `user`.`name`"
    );
    // call MySQL::QueryResult::Error() to check whether there's error or not.
    if (err = query_result.Error())
    {
        std::cout << err << std::endl;
        return 1;
    }
    std::cout << std::setprecision(10);

    // call MySQL::QueryResult::Next() to get next row.
    // MySQL::Row could be cast to bool type indicates whether there
    // are further rows to be fetch or not.
    while (database::MySQL::Row row = query_result.Next())
    {
        // MySQL::Row provides legacy api like MySQL::Row::Int(),MySQL::Row::Int64(),
        // MySQL::Row::Double(),MySQL::Row::String(),etc to fetch data directly.
        // std::int64_t id = row.Get(0).Int64();
        // std::int64_t id = row[0].Int64();

        // But for fluent use and clear code look,
        // it is recommand to use implicit data assigment below.
        // this word properly using SFINAE.
        std::int64_t id = row[0];
        // on c++17 or later,consider using std::string_view for better performance
        // std::string_view name = row[1];
        std::string name = row[1];
        int rank = row[2];
        long double rate = row[3];
        std::cout << id << " " << name << " " << rank << " " << rate << std::endl;
    }

    // for other statement,use MySQL::Exexute.
    // return MySQL::ExecuteResult
    database::MySQL::ExecuteResult execute_result = mysql.Execute(
        R"(INSERT INTO `user`.`name`(`id`, `name`) VALUES (0, 'user_name');)"
    );
    // call MySQL::ExecuteResult::Error() to check whether there's error or not.
    if (err = execute_result.Error())
    {
        std::cout << err << std::endl;
        return 1;
    }
    // call MySQL::ExecuteResult::AffectedRows() to get the number of affected rows.
    std::cout << "affected rows:" << execute_result.AffectedRows() << std::endl;
    return 0;
}

Project

Dependency

mysql C API aslo known as libmysqlclient is required.

Visual Studio Code

This library is coding with Visual Studio Code.With launch.json and tasks.json configured yet
you could open this repository's root in Visual Studio Code (require C++ extension) directly and launch main.cpp
to check MySQL dependecy and for further usage of this library .

Windows

Download MySQL-Community-Server from MySQL official website(https://dev.mysql.com/downloads/mysql/ available on 2022-08-10).
It doesn't whether you use ZIP or MSI Installer.You will find include and lib directory after you decompress or install it. Add the include directory path to system enviroment INCLUDE and the lib directory path to system enviroment INCLUDE.
VS Code does not load system enviroment in real time,you may have to restart vscode.
Finally you could launch (Windows) launch from vscode launch command or press F5 and choose (Windows) launch;

Linux

Install MySQL-Server or libmysqlclient-dev (mysql-devel in CentOS) on you Linux Server using apt(Ubuntu/Debian) or yum(CentOS).
Make sure mysql header files such as mysql/mysql.h exist in you system like /usr/include and libmysqlclient link library
is installed in you system successfully.
Finally you could launch (gdb) launch from vscode launch command or press F5 and choose (gdb) launch;

Usage

MySQL Class

// header defines in "database/mysql.h"
#include "database/mysql.h"

...

// construct mysql.
database::MySQL mysql;

Connect

database::Error err = mysql.Connect(user, pass, host, port, dbname);
if(err) 
{
    // handle err
    std::cout << err <<std::endl;
    return 1;
}

Call database::MySQL::Close() to close mysql connection immediately.
database::MySQL::Close() will also be called when database::MySQL is being destructed.

Query

for select statement,use MySQL::Query

database::MySQL::QueryResult query_result = mysql.Query("select `id`,`name`,`rank`,`rate` from `user`.`name`");
if (err = query_result.Error())
{
    // handle error
    std::cout << err << std::endl;
}else
{
    while (database::MySQL::Row row = query_result.Next())
    {
        // use legacy api
        std::int64_t id = row[0].Int64();
        // implicit assigment for fluent coding.
        std::string name = row[1];
        int rank = row[2];
        long double rate = row[3];
        std::cout << id << " " << name << " " << rank << " " << rate << std::endl;
    }
}

C assert will be called if the index you set in row[index] is bigger than row's total fields number
C assert will also be called if you call MySQL::QueryResult::Next() despite error exists or executing no select statement

Execute

for other statement,use MySQL::Execute()

database::MySQL::ExecuteResult execute_result = mysql.Execute(R"(INSERT INTO `user`.`name`(`id`, `name`) VALUES (0, 'user_name');)");
if (err = execute_result.Error())
{
    //handle error
    std::cout << err << std::endl;
}else{
    std::cout << "affected rows:" << execute_result.AffectedRows() << std::endl;
}