Fundamental of DBMS

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Information about Fundamental of DBMS

Published on December 20, 2007

Author: rapti_2003


DBMS:  DBMS OBJECTIVES: Data Storage Hierarchy Database Models 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: Hierarchical Database. Network Database. Relational Database. 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-child relationship 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) Query Language 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 desired format. It can also instructed to do arithmetic calculations while presentation. Examples of Commercial Systems:  Examples of Commercial Systems Oracle Informix (Unix) DB2, SQL/DS (IBM) Access (Microsoft) SQL Server (Microsoft +) Creating and Using Database :  Creating and Using Database Defining its Structure (Schema). Designing Forms. 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. Automatic Formatting 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 Modifying Record Deleting 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 Language Query by Example. Find :  Find It is use for simple display query. Example: ? 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:- Computer Fundamentals- By-> P.K. Sinha Prepared By: :  Prepared By: Teetas Mukherjee (M.B.A IT) Rai Foundation College Raipur (C.G.) Ph:- 09301412537

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