Datasheet

Oracle consists of many components in addition to the database engine, including components that
perform data analysis, help you manage XML and image data, manage applications and clusters, and
monitor and manage database performance. However, those components are beyond the scope of this
book, which focuses on the components that make up an Oracle database.
Because Oracle is a relational database, it contains numerous components, and each component contains
many objects. In this section, you look at the main objects that make up an Oracle database. While the
topics presented here provide only a cursory overview, this information will help you throughout the
rest of the book.
The following sections describe the five file types created when you create an Oracle database.
Data files
Data files are perhaps the most important files that make up your database and perhaps among the most
complex. When an Oracle database is created, a single data file is created. However, you can create mul-
tiple data files, and most typical production databases contain at least two data files.
Data files are complex because they contain the various objects that make up your database. In Oracle ter-
minology, these objects are known as segments. Because of the complexities of an Oracle data file, Table 1-2
contains only a partial list of the various objects, which you can compare to SQL Server data files.
Table 1-2: Oracle Data File Objects
Object Description
Tables Contains the data in a database, organized in a row-column format.
Keys Primary keys provide a unique value for each row of data in a table.
Foreign keys provide a relationship between two tables using a
column in one table and the primary key in another table.
Indexes Provides pointers to rows in a table similar to the fashion that the
index in this book provides pointers to specific topics.
Constraints Provides a means by which you can enforce the integrity of a
database, such as not allowing a column to contain a NULL value.
Stored Procedures A group of SQL statements compiled into a single execution plan.
Views A SQL SELECT statement that returns a virtual table.
Triggers A special class of stored procedures that are automatically executed
when an
Insert, Update, or Delete statement is executed
against a table.
Functions A group of SQL statements that can be encapsulated into a subroutine
that can be called by views and stored procedures.
User Identifies a user with a database.
Roles A group containing certain permissions in the database to which you
add users, effectively assigning the same permissions to each user.
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