In the previous chapter, we learned how to create a login page from scratch. However, it is not functional yet, as the login page is not connected to a database. In this chapter, you will learn how to connect your Qt application to a MySQL (or MariaDB) database that validates login credentials.
We will walk through this chapter in a step-by-step approach to discover the powerful features that come with Qt and allow your application to connect directly to a database without any additional third-party dependencies. Database querying is a huge topic by itself, but we will be able to learn the most basic commands from scratch through examples and practical methods.
Two of the most popular ones are MySQL and SQLite. The SQLite database is usually used offline and it doesn't require any setup as it uses an on-disk file format for storing data. Therefore, in this chapter, we will learn how to set up a MySQL database system instead, and at the same time learn how to connect our Qt application to a MySQL database. The C++ code used to connect to the MySQL database can be reused for connecting to other database systems without many alterations.
MySQL is an open source database management system based on the relational model, which is the most common method used by modern database systems to store information for various purposes.
Unlike some other legacy modelsāsuch as an object database system or a hierarchical database systemāthe relational model has been proven to be more user friendly and performs well beyond the other models. That's the reason why most of the modern database systems we see today are mostly using this method.
MySQL was originally developed by a Swedish company called MySQL AB, and its name is the combination of My, the name of the daughter of the company's co-founder, and SQL, the abbreviation for Structured Query Language.
Similar to Qt, MySQL has also been owned by multiple different people throughout its history. The most notable acquisition happened in 2008, where Sun Microsystems bought MySQL AB for $1 billion. One year later in 2009, Oracle Corporation acquired Sun Microsystems, and so MySQL is owned by Oracle up to this day. Even though MySQL changed hands several times, it still remains as an open source software that allows users to change the code to suit their own purposes.
Due to its open source nature, there are also other database systems out there that were derived/forked from the MySQL project, such as MariaDB, Percona Server, and so on. However, these alternatives are not fully compatible with MySQL as they have modified it to suit their own needs, and therefore some of the commands may be varied among these systems.
According to a 2017 survey carried out by Stack Overflow, MySQL is the most widely used database system among web developers, as we can see in the following screenshot:
The survey result indicates that what you learn in this chapter can be applied to not just Qt projects but also web, mobile app, and other types of applications.
Furthermore, MySQL and its variants are being used by big corporations and project groups such as Facebook, YouTube, Twitter, NASA, Wordpress, Drupal, Airbnb, Spotify, and so on and so forth. This means that you can easily get answers when encountering any technical issues during development.
For more information regarding MySQL, please visit:
https://www.mysql.com
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There are many different ways to set up your MySQL database. It really depends on the type of platforms you are running, whether it is Windows, Linux, Mac, or any other type of operating system; it will also depend on the purpose of your databaseāwhether it's for development and testing, or for a large-scale production server.
For large scale services (such as social media), the best way is to compile MySQL from the source, because such as project requires a ton of optimization, configuration, and sometimes customization in order to handle the large amount of users and traffic.
However, you can just download the pre-compiled binaries if you're going for normal use, as the default configuration is pretty sufficient for that. You can install a standalone MySQL installer from their official website or the download installation packages that come with several other pieces of software besides MySQL.
In this chapter, we will be using a software package called XAMPP, which is a web server stack package developed by a group called Apache Friends. This package comes with Apache, MariaDB, PHP, and other optional services that you can add on during the installation process. Previously, MySQL was part of the package, but it has since been replaced with MariaDB starting from version 5.5.30 and 5.6.14. MariaDB works almost the same as MySQL, except those commands involving advanced features, which we will not be using in this book.
The reason why we use XAMPP is that it has a control panel that can easily start and stop the services without using Command Prompt, and provides easy access to the configuration files without you having to dig into the installation directory by yourself. It is very quick and efficient for application development that involves frequent testings. However, it is not recommended that you use XAMPP on a production server as some of the security features have been disabled by default.
Alternatively, you may also install MySQL through other similar software packages such as AppServ, AMPPS, LAMP (Linux only), WAMP (Windows only), ZendServer, and so on.
Now, let's learn how to install XAMPP:
- First, go to their website at https://www.apachefriends.org and click on one of the download buttons located at the bottom of your screen, w...
