Database Reference
In-Depth Information
•
Availability
:
Server databases are intended for enterprises, so they need to be
available 24/7. To be available all the time, server databases come with some high-
availability features, such as mirroring and log shipping.
•
Performance
:
Server databases usually have huge hardware support, so servers
running these databases have large amounts of RAM and multiple CPUs. This is
why server databases support rich infrastructure and give optimum performance.
•
Scalability
:
This property allows a server database to expand its ability to process
and store records even if it has grown tremendously.
The Database Life Cycle
The database life cycle defines the complete process from conception to implementation. The
development and implementation processes of this cycle can be divided into small phases; only after
completing each phase can you move on to the next.
Before getting into the development of any system, you need to have strong a life-cycle model to
follow. The model must have all the phases defined in the proper sequence, which will help the
development team build the system with fewer problems and full functionality as expected.
The database life cycle consists of the following stages, from the basic steps involved in designing a
global schema of the database to database implementation and maintenance:
•
Requirements analysis
:
Requirements need to be determined before you can begin
design and implementation. The requirements can be gathered by interviewing
both the producer and the user of the data; this process helps in creating a formal
requirement specification.
•
Logical design
:
After requirements gathering, data and relationships need to be
defined using a conceptual data modeling technique such as an entity-
relationship (ER) diagram. This diagram shows how one object will connect to the
other one and by what relationship (one-one or one-many). Relationships are
explained later in this chapter.
•
Physical design
:
Once the logical design is in place, the next step is to produce the
physical structure for the database. The physical design phase involves creating
tables and selecting indexes. An introduction to indexes is out of this topic's scope,
but an index is basically like an index of a book, which allows you to jump to a
particular page based on the topic of your choice and helps you avoid shuffling all
the pages of the topic to reach the page of interest. Database indexes do
something similar; they manage and maintain the order of rows when inserted
into the table, which helps SQL queries pull data fast based on a provided value for
the index column.
Database implementation
:
Once the design is completed, the database can be
created through the implementation of formal schema using the data definition
language (DDL) of the RDBMS. The DDL consists of the statements that play key
roles in creating, modifying, and deleting the database or database objects.
CREATE
,
ALTER
, and
DROP
are prime examples of a DDL.
