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MariaDb Essentials
MariaDb Essentials

MariaDb Essentials: Quickly get up to speed with MariaDB—the leading, drop-in replacement for MySQL, through this practical tutorial

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MariaDb Essentials

Chapter 2. Databases and Tables

In the previous chapter, we learned how to install and update MariaDB, and we started playing with mysql, its command-line client. In this chapter, we will learn how to create the data structures on which we want to work. We will use the MariaDB server that we installed in the previous chapter, and use the already explained command-line client. We will also create an example database that will be used in the rest of the book.

In particular, we will cover the following topics:

  • Working with databases
  • Working with tables
  • Data types
  • Character sets and collations
  • Storage engines
  • Indexing
  • Using comments
  • Working with metadata
  • Creating an install script

Working with databases

An RDBMS allows you to store data in a structured way, with relations between the different data collections. These collections of data are stored in tables. However, each table is located in a database. We can see this structure as a container for tables and other objects. In MariaDB, schema is a synonym for database and is used in the documentation as well as in the statement syntax.

To list the existing databases, we can use the SHOW DATABASES statement. Let's try it on our newly installed MariaDB:

MariaDB [(none)]> SHOW DATABASES;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| mysql              |
| test               |
+--------------------+
3 rows in set (0.09 sec)

As we can see in this code snippet, there are several built-in databases. They are as follows:

  • information_schema: A virtual database containing various meta-information about our data structures and server usage. It can be read, but not directly...

Working with tables

Now we are going to create the necessary tables. First, we will run the USE statement to set eshop as our default database. This allows us to avoid specifying the database name in each statement, as explained in Chapter 1, Installing MariaDB.

MariaDB [(none)]> USE eshop;
Database changed

Then we can create our first table using CREATE TABLE. This command specifies concepts that have not yet been discussed, such as table types and storage engines. The following example shows the syntax of the statement, but we will leave out the details for now. All these concepts will be made clear by the end of this chapter.

CREATE TABLE catalogue
(
  id INTEGER UNSIGNED NOT NULL AUTO_INCREMENT,
  name VARCHAR(50) NOT NULL,
  price DECIMAL(6, 2) NULL,
  quantity SMALLINT NOT NULL DEFAULT 0,
  description TEXT NOT NULL,
  PRIMARY KEY (id)
)
  ENGINE = InnoDB
  COMMENT 'Catalogue of products on sale';

While the details are probably a bit obscure, the general syntax of the statement...

Working with columns

A table row can be seen as a collection of named properties are called columns or fields. So, columns must suit the units of data that make up the information.

In the previous sections, we learned the most important SQL statements for managing databases and tables. We have also seen some example column definitions. In this section, we will discuss the following:

  • Column definitions
  • The management of columns

A column definition has the following syntax:

<column_name> <data_type> [type_attributes] [NULL | NOT NULL]
[DEFAULT <value>] [AUTO_INCREMENT] [COMMENT 'string']

The following subsections will explain the data types, the NULL attribute, and the default values. The AUTO_INCREMENT attribute and comments will be discussed later in the indexing section of this chapter.

Data types

The data type is the most important characteristic that we need to set: it determines the class of data that the column will contain, its size, the way it will be stored...

Storage engines

MariaDB does not directly write or read table data. Such operations are delegated to a special type of plugin called storage engines. This is the same mechanism that is used in MySQL. In fact, storage engines written for MySQL can be recompiled against MariaDB, and vice versa.

Storage engines can also support features that are not directly supported by the server. For example:

  • Transactions
  • Data and index caches
  • Foreign keys

When we create a table, we should decide which storage engine will be used for handling the table. We can then specify it with the ENGINE table option, as we did in the Working with Tables section:

CREATE TABLE table_name
(
  ...
)
  ENGINE = InnoDB;

The preceding clause is optional. If it is not specified, the @@storage_engine server variable will determine the storage engine to be used. This variable can also be set per session. By default, it is set to InnoDB:

MariaDB [(none)]> SELECT @@storage_engine;
+------------------+
| @@storage_engine |
+-------...

Indexing

Operations on databases can be complex. Often, MariaDB has to examine several data to find the rows that we want to read. It may also have to perform complex operations, such as aggregating data or sorting values. Typical operations on data will be described in Chapter 3, Getting Started with SQL. Here we will briefly discuss the data structure used to optimize these operations—that is, indexes. Key is a synonym for index.

Note

Note that different storage engines implement indexes in different ways. The following discussion refers to InnoDB, which is the most commonly used engine. If we use other engines, such as MEMORY or MyISAM, we may need to check the MariaDB KnowledgeBase to learn how these engines handle indexes.

To explain what an index is, we are going to use a typical example: a book's index. Imagine we have to find a topic, or some specific information, in a big book that we have never read before, and which does not have an index. We would need a lot of time...

Working with databases


An RDBMS allows you to store data in a structured way, with relations between the different data collections. These collections of data are stored in tables. However, each table is located in a database. We can see this structure as a container for tables and other objects. In MariaDB, schema is a synonym for database and is used in the documentation as well as in the statement syntax.

To list the existing databases, we can use the SHOW DATABASES statement. Let's try it on our newly installed MariaDB:

MariaDB [(none)]> SHOW DATABASES;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| mysql              |
| test               |
+--------------------+
3 rows in set (0.09 sec)

As we can see in this code snippet, there are several built-in databases. They are as follows:

  • information_schema: A virtual database containing various meta-information about our data structures and server usage. It can be read, but not directly modified...

Working with tables


Now we are going to create the necessary tables. First, we will run the USE statement to set eshop as our default database. This allows us to avoid specifying the database name in each statement, as explained in Chapter 1, Installing MariaDB.

MariaDB [(none)]> USE eshop;
Database changed

Then we can create our first table using CREATE TABLE. This command specifies concepts that have not yet been discussed, such as table types and storage engines. The following example shows the syntax of the statement, but we will leave out the details for now. All these concepts will be made clear by the end of this chapter.

CREATE TABLE catalogue
(
  id INTEGER UNSIGNED NOT NULL AUTO_INCREMENT,
  name VARCHAR(50) NOT NULL,
  price DECIMAL(6, 2) NULL,
  quantity SMALLINT NOT NULL DEFAULT 0,
  description TEXT NOT NULL,
  PRIMARY KEY (id)
)
  ENGINE = InnoDB
  COMMENT 'Catalogue of products on sale';

While the details are probably a bit obscure, the general syntax of the statement...

Working with columns


A table row can be seen as a collection of named properties are called columns or fields. So, columns must suit the units of data that make up the information.

In the previous sections, we learned the most important SQL statements for managing databases and tables. We have also seen some example column definitions. In this section, we will discuss the following:

  • Column definitions

  • The management of columns

A column definition has the following syntax:

<column_name> <data_type> [type_attributes] [NULL | NOT NULL]
[DEFAULT <value>] [AUTO_INCREMENT] [COMMENT 'string']

The following subsections will explain the data types, the NULL attribute, and the default values. The AUTO_INCREMENT attribute and comments will be discussed later in the indexing section of this chapter.

Data types

The data type is the most important characteristic that we need to set: it determines the class of data that the column will contain, its size, the way it will be stored, and the operations...

Storage engines


MariaDB does not directly write or read table data. Such operations are delegated to a special type of plugin called storage engines. This is the same mechanism that is used in MySQL. In fact, storage engines written for MySQL can be recompiled against MariaDB, and vice versa.

Storage engines can also support features that are not directly supported by the server. For example:

  • Transactions

  • Data and index caches

  • Foreign keys

When we create a table, we should decide which storage engine will be used for handling the table. We can then specify it with the ENGINE table option, as we did in the Working with Tables section:

CREATE TABLE table_name
(
  ...
)
  ENGINE = InnoDB;

The preceding clause is optional. If it is not specified, the @@storage_engine server variable will determine the storage engine to be used. This variable can also be set per session. By default, it is set to InnoDB:

MariaDB [(none)]> SELECT @@storage_engine;
+------------------+
| @@storage_engine |
+-------...
Left arrow icon Right arrow icon

Key benefits

  • 1. Get to know the basic SQL queries so you can quickly start using MariaDB
  • 2. Take control of your data through the advanced features of MariaDB
  • 3. Exploit the full potential of MariaDB’s exclusive features through quick, practical examples

Description

This book will take you through all the nitty-gritty parts of MariaDB, right from the creation of your database all the way to using MariaDB’s advanced features. At the very beginning, we show you the basics, that is, how to install MariaDB. Then, we walk you through the databases and tables of MariaDB, and introduce SQL in MariaDB. You will learn about all the features that have been added in MariaDB but are absent in MySQL. Moving on, you’ll learn to import and export data, views, virtual columns, and dynamic columns in MariaDB. Then, you’ll get to grips with full-text searches and queries in MariaDb. You’ll also be familiarized with the CONNECT storage engine. At the end of the book, you’ll be introduced to the community of MariaDB.

Who is this book for?

If you don't know the SQL language, but you want to quickly jump into the SQL world and learn how to use MariaDB, or if you already know how to use MySQL but you want to go further, then this book is ideal for you.

What you will learn

  • 1. Install and configure MariaDB
  • 2. Create databases, tables, and indexes
  • 3. Import and export data from and to external files
  • 4. Work with views and virtual columns
  • 5. Create, read, update, and delete records in your database
  • 6. Use dynamic columns
  • 7. Set up a powerful full-text search system
  • 8. Access your external data from MariaDB through the CONNECT engine

Product Details

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Publication date, Length, Edition, Language, ISBN-13
Publication date : Oct 27, 2015
Length: 206 pages
Edition : 1st
Language : English
ISBN-13 : 9781783982868
Category :
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Length: 206 pages
Edition : 1st
Language : English
ISBN-13 : 9781783982868
Category :
Tools :

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Table of Contents

9 Chapters
1. Installing MariaDB Chevron down icon Chevron up icon
2. Databases and Tables Chevron down icon Chevron up icon
3. Getting Started with SQL Chevron down icon Chevron up icon
4. Importing and Exporting Data Chevron down icon Chevron up icon
5. Views and Virtual Columns Chevron down icon Chevron up icon
6. Dynamic Columns Chevron down icon Chevron up icon
7. Full-Text Searches Chevron down icon Chevron up icon
8. Using the CONNECT Storage Engine Chevron down icon Chevron up icon
Index Chevron down icon Chevron up icon

Customer reviews

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Amazon Customer Aug 22, 2021
Full star icon Full star icon Full star icon Full star icon Full star icon 5
Another Packt title and in a similar vein to others I've read - an easy read and well written. I knew nothing of the subject and found the work perfectly suited to my needs.
Amazon Verified review Amazon
S. Keay Jun 11, 2017
Full star icon Full star icon Full star icon Full star icon Empty star icon 4
Just what I was after
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