Data Storage Hierarchy
Database Components Data Storage Hierarchy: Data Storage Hierarchy Bit: it is smallest unit of data a single binary Digit.
Character: Multiple related bits are combine to form a character(M,8,$..etc).
Field: Multiple related character are combine to form field. (employee code, emp name).
Record: Multiple related field are combined to form record. (a student record will contain field containing data of the students)
Data Storage Hierarchy: Data Storage Hierarchy File: Multiple related file are combine to form a file.(a collection of all employee record of a company will be employee file.)
Database: Multiple related file are integrated to form a Database. (multiple employee file such as salary file, Personnel information file, Skill Set file)
DATABASE MODEL : DATABASE MODEL A database model defines the
manner in which the various files of a
database are linked together. The
commonly used database model are:
Object Oriented Database. HIERARCHICAL DATABASE MODEL : HIERARCHICAL DATABASE MODEL The data element are linked in form of inverted tree structure.
Root at the top.
Parent data element is one and can have one or more subordinate or child element.
There may be many child but only one parent data element.
HIERARCHICAL DATABASE MODEL : HIERARCHICAL DATABASE MODEL The data element of many applications can be neatly organised with this model
The main limitation is, it does not support flexible data access because the data can only be accessed by following the tree structure.
Hence the mapping of data and their relationship in tree structure is very important when the database is first design.
NETWORK DATABASE MODEL : NETWORK DATABASE MODEL It is extension of Hierarchical Database model.
It follows parent-child relationship.
the mapping of data and their relationship is very important when the database is first design.
Here the child data can have more than one parent and can have no parent at all.
Here the extraction of information can be from any data element in database structure instead of root data element. RELATIONAL DATABASE MODEL : RELATIONAL DATABASE MODEL Here the data element are organised in form of multiple tables with rows and columns.
Each table represents separate file.
Each table column are represent as field.
Each table row are represent as data record.
The data in one table are related to data in another table by common field. RELATIONAL DATABASE MODEL : RELATIONAL DATABASE MODEL It provide grater flexibility in data organisation and future enhancement.
If new data is to be added then it is not necessary to redesign the database rather new table can be easily added. DATABASE MODEL : DATABASE MODEL SOME LIMITATION OF DATABASE MODELS ARE:
Ability to model complex nested entities such as engineering objects, multimedia documents.
Have only a limited set of data types they do not allow storage and retrieval of long unstructured data such as images, audio and textual documents. Object-Oriented DATABASE MODEL : Object-Oriented DATABASE MODEL It was introduced to overcome the above listed shortcoming.
IT is a collection of object whose behavior, state and relationship is defined according to object oriented concept. Object-Oriented DATABASE MODEL : Object-Oriented DATABASE MODEL Main Components of DBMS: : Main Components of DBMS: Data Definition Language (DDL).
Data Manipulation Language (DML)
Report Generator. Data Definition Language (DDL). : Data Definition Language (DDL). IT is use to define the structure of a
Database. The database structure definition
(Schema) typically includes the following:
Defining all data element.
Defining data element field and records.
Defining the name, field length, and field type for each data type.
Defining control for field that can have only selective values.
Defining the logical relationship among various data element.
Defining access control for security purpose. Data Definition Language (DDL). : Data Definition Language (DDL). In short every thing about the database
structure is included in its schema.
This description can be use by system
analyst in defining new application.
It is possible to generate complete description from its schema.
Database Administrator : Database Administrator Database system are typically installed and
coordinated by an individual called database
Administrator. He have the overall authority
to establish and control data definition and
Standard. he is responsible for determining
relationship among data element and
designing database security. He also train
programmer to use database. A DATA
DICTONARY is develop to store DDL and
even it is automatically updated by DDL
module. Data Manipulation Language (DML) : Data Manipulation Language (DML) Once the structure is defined the database is
ready for entry and manipulation of data.
Data Manipulation Language (DML) includes
the command to enter and manipulate the
Data, with these commands the user can
Add new records, navigate through the existing records, view contents of various fields, modify the data, delete the existing record, sort the record in desired sequence.
QUERY LANGUAGE : QUERY LANGUAGE all database provide a query language
which is use to define the requirement
for extracting information from the
database in form of Queries. Report Generator : Report Generator It helps the user to design report in
It can also instructed to do arithmetic
calculations while presentation. Examples of Commercial Systems: Examples of Commercial Systems Oracle
DB2, SQL/DS (IBM)
SQL Server (Microsoft +) Creating and Using Database : Creating and Using Database Defining its Structure (Schema).
Entering Data in it. Defining its Structure (Schema). : Defining its Structure (Schema). Here we list down all the field required in a database.
Determine name type and size of each field.
This information is captured in the system by the tool called schema builder. (schema builder help the user to define the database schema by prompting the user to enter the field type, field size and so on…)
Modification is always possible be it is always better to design the database carefully in 1st instance and minimize the need to modify. Designing Forms : Designing Forms To Facilitate easier data entry form are
form design with several feature:
List Box: it list several option and the user can choose among them.
Validation check:to ensure the corectness of entered data.
Automatic conversions: like upper to lower case.
Designing Forms : Designing Forms
Entering Data : Entering Data After the form have been designed,
the database is ready for entry of data
Data is entered one record at a time.
First the form with blank field are
Displayed then user key in data in the
blank form, then for second record and
so on…… Viewing, Modifying, Deleting and Adding records : Viewing, Modifying, Deleting and Adding records Viewing Record
Adding Record Viewing records : Viewing records The command for viewing a record
enables the user to display the record
of various field according to the user
requirement Modifying records : Modifying records The command for modifying a record
enables the user not only view but also
update the various field of a record. Delete records : Delete records The command for delete a record
enables the user to remove the
selected data from the database. Add records : Add records The command for ADD a record
enables the user to add new record to
Database when this command is
enabled the system display a blank
form and wait for the user to fill it Searching for Desired Information. : Searching for Desired Information. Find Command.
Query by Example. Find : Find It is use for simple display query.
It can not be use for complex query.
It can operate only one table at a time. Query Language : Query Language For handling complex queries all
database support a query language.
Query lang can be easily learnt and
used even by non programmer. It can
operate on multiple tables at a time and
specified criteria can be saved for future
Use. Query By Example : Query By Example It is a form which is designed to collect all
necessary information and the user simply
have to specify the search criteria by
inputting values in the field of this form.
again the values may be typed or selected
from the set of options. Once the user
complete the QBE form the QBE engine
automatically convert in suitable Query
language. Reference:- : Reference:- Books:-
By-> P.K. Sinha
Prepared By: : Prepared By: Teetas Mukherjee
Rai Foundation College