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LPI Linux Certification in a Nutshell, 3rd Edition by James Stanger, Bruno Gomes Pessanha, Stephen Addison Schneiter, Adam Haeder

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Database Overview

A full understanding of database management recommendations and design methodology is outside the scope of this book and outside the scope of the LPI 102 exam. However, you will need to know the basics of storing data in a MySQL table, managing that data (adding, updating, and deleting), and performing relatively complex queries on that data.

A MySQL server instance allows the creation and access of multiple databases simultaneously. The MySQL server actually creates a directory in the filesystem for each new database created. Each database may contain many tables, the layout of which is set upon initial table creation, but can be modified later. Although there are many options and pros and cons regarding database formats and storage engines, for the purposes of the LPI 102 exam we will assume the default storage engine (MyISAM) and concern ourselves more with table layout and querying. For more information on storage engines and other advanced MySQL topics, visit http://dev.mysql.com/doc/.

A table is made up of a number of columns, each given a certain datatype that defines what data may be stored in this column. Table 13-2 describes some of the more common MySQL datatypes.

Table 13-2. Common MySQL datatypes

Datatype

Description

INTEGER

A normal-size integer. The signed range is –2147483648 to 2147483647. The unsigned range is 0 to 4294967295.

FLOAT

A floating-point number.

BOOLEAN

Stored as a single character integer. A value of zero is considered false. Nonzero values ...

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