The main point of a database is data. In Part II, you learned how to create and alter tables. As interesting as that may have been, the data that will go in tables is essential. If you felt a little confused when creating and altering tables in the previous chapters, it may be because it’s difficult to envision how tables and their columns will come into play with data, without having more experience adding data.
In this part, we will explore some of the fundamental ways in which
data may be entered into a database and inserted into tables. This will be
covered in Chapter 6, Inserting Data. It primarily involves the
INSERT statement. The SQL statement for retrieving data from
tables is the SELECT statement, which is covered extensively
in Chapter 7, Selecting Data.
You’ve seen both of these SQL statements in use several times in the
previous chapters. However, in the next two chapters you will learn more
about the various syntax and options for each of them, and you will be
given plenty of practical examples of their use.
Data often needs to be changed and sometimes deleted, so in Chapter 8, Updating and Deleting Data we’ll take a
look at how to update and delete data. This chapter will help you to learn
how to use the UPDATE and the DELETE statements
to do these common tasks. These are important for managing data in a
database.
The final chapter of this part, Chapter 9, Joining and Subquerying Data, is an advanced one. It’s not too difficult to follow, but you should definitely not rush through it. In it, you will learn how to select data from one or more tables, and to use that data as a basis for inserting, selecting, updating, or deleting data in other tables. Thus, you should make sure that you’ve mastered the material in the previous chapters before skipping ahead to Chapter 9.
In each chapter of this part, there are practical examples that are used to explain the various SQL statements and related factors. You should enter those examples into your server. Even if you are reading this book from a digital version on your computer, I recommend highly that you manually type all of the SQL statements you are instructed to enter. It may seem like a little thing, but the process of typing them will aid your learning process and help you remember the syntax and the deviations of each SQL statement. When you make a mistake and type something incorrectly, you’ll get an error message. Deciphering error messages is part of being a good MySQL and MariaDB developer. If you copy and paste everything as I present it to you, you will only confirm the accuracy of the book’s examples, and you will learn only a little. It’s easy to learn when you don’t make any mistakes. It’s more difficult, but you will learn more when you manually enter the SQL statements and get errors and then have to determine where you went wrong.
At the end of each chapter of this part, as with almost all of the chapters in this book, there are exercises. For the same reasons that you should enter the SQL statements in the examples throughout the chapters, you should also complete the exercises. This is not just a book to be read. It’s meant to be a tool to help you to learn MySQL and MariaDB. To accomplish that, you must do more than just read the chapters: you need to participate, experiment, and research. If you make this kind of effort, you will benefit greatly from this book. This is probably the most essential part of the book, so you should fully engage with these concluding chapters.