Implementing a Relational Database:
For implementing a relational database you have to perform different tasks. The relational database model is used to
express the database design.
The following tasks are performed to design the
database and to implement it.
Defining the Database Structure:
Defining the database structure is the most important task for implementing the
relational database. Some DBMS products
require a text file that describes the data structure. The database definition
language is used to describe the database structure. In database structure, the
tables, columns of each table, indexes, constraints and security restrictions
are defined. Some DBMSs provide the graphical user-interface to define the
structure of database (instead of providing a text file containing DDL
statements for database structure). The example of such DBMS is Ms-Access. It
provides very easy and quick way to define the structure of database. In
general, graphical definition tools are common for DBMS that are used in
personal computers. The DBMS used on servers and mainframes use both graphical
definition tools and DDL text files, to define the database structure. The
examples of these DBMSs are ORACLE and SQL server.
A DDL text file example is given below, which
defines the structure of simple relational database "college".
Create Schema College
Create Table Student
(
Roll_No Integer NOT NULL
Name VarChar(20) NOT NULL
Address VarChar(35) NOT NULL
Marks Integer NOT NULL
PRIMARY KEY (Roll No)
)
Some DBMS products also provide the facilities to
define passwords and other security features.
Allocating Physical Media:
In addition to define the structure of database,
you must have to allocate database structures to physical media. For example, in
personal database system, the database name, directory name with complete path,
is assigned. The DBMS then allocates storage space automatically.
The DBMSs used on servers and mainframes must be
carefully planned to control and to distribute data across disks and channels.
The larger size, faster disk and better channel, improve the accessing speed of
data from database.
In addition to specify the location and amount of
space for user's data, the database designer may also need to declare whether or
not the file space should be increased as needed. Typically, the amount of space
is expressed as either a specific amount or as a percentage of the initial
space.
Creating the Database Data:
Once the database has been defined and allocated
to physical storage, the data is entered into it. Different ways are used to
populate the database. The most common way to enter data into database is by
using application programs.
Once data is entered into database, it must be
verified for accuracy. You cat verify data of database manually by making
printout of the data. It is very time consuming and expensive method. Mostly the
application programs are developed o verify the data automatically. Similarly,
the constraint rules are applied on the database, so that the correct data could
be entered by end-users.
Relational Data Manipulation:
Once the database is populated with data, the
users must have some means to manipulate the data of database. Typically, data
manipulation includes, retrieval insertion, deletion, and modification of data.
The data manipulation language (DML) is used for data manipulation.
Creating Database Maintenance Plan:
A maintenance plan is a schedule of activities to
be performed after implementing the database. Such activities include backing up
the database, checking for violations of referential integrity, optimizing disk
space for user data and indices etc. The maintenance plan should be developed
when the database is created.
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