tag:blogger.com,1999:blog-42794710563179101622024-03-13T07:58:45.764-07:00DATABASE CONCEPTSDatabase is used to store, manipulate and retrieve data in every type of organization like Business, Healthcare, Education, Govt and Libraries. Database technology is used by Individuals like Personal Computers, or by working groups Like Department wise, and Enterprise wise and Distributed wise.firendzhttp://www.blogger.com/profile/15283816516424557590noreply@blogger.comBlogger14125tag:blogger.com,1999:blog-4279471056317910162.post-63241338084263329062012-01-22T01:39:00.000-08:002012-01-22T01:39:26.237-08:00Structure of DBMS<div dir="ltr" style="text-align: left;" trbidi="on"><br />
<div class="MsoNormal"><b><u><span style="font-size: 14.0pt; mso-bidi-font-size: 12.0pt;">Structure of DBMS <o:p></o:p></span></u></b></div><div class="MsoNormal"><br />
</div><div class="MsoNormal" style="line-height: 150%; text-align: justify;">The structure of <b><a href="file:///D:/mamatha%20ibg/DBMS.doc">DBMS</a> </b>typically based on the relational data model . The following diagram shows typically DBMS based on the relational data model. The DBMS access <b>SQL </b>commands and generated a form of variety of user interfaces and produce <b>query </b>evaluation plan , Executes these plans against the database and returns the answers. When a user issues a query ,the parser can receive the query and it is presented to query optimizer which uses information about how data is stored in the database and produce efficient execution plan for evaluating the query operator. An execution plan is the <b>blue print</b> for evaluate in the query and usually representation as a pre of relational operator.</div><div class="MsoNormal" style="line-height: 150%; text-align: justify;"><br />
</div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjHV4X_I0MawlrwlpiFOvBI4mSKOONI2HtVBB-aaL37Xn510-xKRvzVSDT_zcizUGJQY0L8n4FYQhU2beaXw4AcEuD-9qonzAuZbgRSvGs16HVapoXBzT9HqzXb4_h9NOFZUP6dvCRN9KGY/s1600/miming.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjHV4X_I0MawlrwlpiFOvBI4mSKOONI2HtVBB-aaL37Xn510-xKRvzVSDT_zcizUGJQY0L8n4FYQhU2beaXw4AcEuD-9qonzAuZbgRSvGs16HVapoXBzT9HqzXb4_h9NOFZUP6dvCRN9KGY/s1600/miming.jpg" /></a></div><div class="MsoNormal" style="line-height: 150%; text-align: justify;"><br />
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</div><div class="MsoNormal" style="line-height: 150%; text-align: justify;"> The code that implements with relational operator on the top of the file access methods layer. This layer includes a variety of software for supporting of concepts of files, in DBMS file is collection of records or pages. This layer typically supports as a <b>heap file </b> as well as Indexing in addition to keeping the track of records or pages in a file. In this layer organize the information with in the pages. The file and access methods layer code sits on the top of the <b>buffer manager </b> , which brings pages in from the disk to main memory . The main memory has needed in response to read requests.</div><div class="MsoNormal" style="line-height: 150%; text-align: justify;"> The lowest layer of DBMS <b>software </b> management space on disk where the data is stored and high layer allocated and reallocated read and write pages through this layer can call the disk manager. In DBMS supports <b>concurrency</b> <b>control</b> and <b>crash recovery manager</b> by carefully scheduling user request and maintain a <b>log of requests</b> in database. <b><a href="file:///D:/mamatha%20ibg/MAJOR%20COMPONENDS.doc">DBMS components</a> </b>associated with concurrency control and recovery includes the transaction manager which ensures that transaction requests end release logs to a suitable locking <b>protocol</b> and schedule the execution transaction.</div></div>firendzhttp://www.blogger.com/profile/15283816516424557590noreply@blogger.com1tag:blogger.com,1999:blog-4279471056317910162.post-13853714957284861632012-01-22T01:36:00.000-08:002012-01-22T01:36:52.790-08:00STRATEGY OF DATABASE PLANNING:<div dir="ltr" style="text-align: left;" trbidi="on"><br />
<div class="MsoNormal"><b><i><u>STRATEGY OF DATABASE PLANNING:</u></i></b> </div><div class="MsoNormal"><br />
</div><div class="MsoNormal" style="line-height: 150%; text-align: justify;">Data must be viewed as a corporate resource and other corporate resources must be devoted to the development, implement and use of one or more databases. Database planning is strategy corporate effort to determine the information needs of the organization form extended period into the future. A successful database planning project will precede operational project to design and implement new databases to satisfy the organizational information needs.</div><div class="MsoNormal" style="line-height: 150%; text-align: justify;"><i><u>The need for database planning:</u></i> Database planning is directed by the information needs of the organization which in turn or determined by the company’s <b>business plan</b> . the process is shown in the below diagram.</div><div class="MsoNormal" style="line-height: 150%; text-align: justify;"><span style="color: purple; font-size: large;"><b>Business Plan </b><b><span style="font-family: Wingdings; mso-ascii-font-family: "Times New Roman"; mso-char-type: symbol; mso-hansi-font-family: "Times New Roman"; mso-symbol-font-family: Wingdings;">à</span> Information Needs </b><b><span style="font-family: Wingdings; mso-ascii-font-family: "Times New Roman"; mso-char-type: symbol; mso-hansi-font-family: "Times New Roman"; mso-symbol-font-family: Wingdings;">à</span> Database Plan </b></span><b><span style="font-size: large;"><span style="color: purple;"><span style="font-family: Wingdings; mso-ascii-font-family: "Times New Roman"; mso-char-type: symbol; mso-hansi-font-family: "Times New Roman"; mso-symbol-font-family: Wingdings;">à</span> Database Development Projects</span>.</span><o:p></o:p></b></div><div class="MsoNormal" style="line-height: 150%; text-align: justify;">The corporation formulates has its strategy business plan for the next 5 (five) years . Accomplishing the objectives of this plans depends on the availability of certain identify types of information . The information can we obtained only if the data sources are identified in the database planning, or in place . This indicates the needs of the database development projects which create new database or enhance or integrate existing databases. <i>Database planning has significant advantages</i> <u>James cites </u> several advantages of formal information resource plan.</div><ol start="1" style="margin-top: 0in;" type="1"><li class="MsoNormal" style="line-height: 150%; mso-list: l0 level1 lfo1; tab-stops: list .5in; text-align: justify;">It expresses management current understanding of the information resources.</li>
<li class="MsoNormal" style="line-height: 150%; mso-list: l0 level1 lfo1; tab-stops: list .5in; text-align: justify;">It identifies and justifies resources requirements, helping ensure that the resources will be available.</li>
<li class="MsoNormal" style="line-height: 150%; mso-list: l0 level1 lfo1; tab-stops: list .5in; text-align: justify;">It identifies and justifies for effective resources management including the collaboration among departments or diligence with in the organization.</li>
<li class="MsoNormal" style="line-height: 150%; mso-list: l0 level1 lfo1; tab-stops: list .5in; text-align: justify;">It Specifies action plans for achieving objectives.</li>
<li class="MsoNormal" style="line-height: 150%; mso-list: l0 level1 lfo1; tab-stops: list .5in; text-align: justify;">It can provide a powerful stimulus and sense of direction to employees at all levels. </li>
</ol><div class="MsoNormal" style="line-height: 150%; margin-left: .25in; text-align: justify;">Focusing these effects increasing their productivity and making them feel that they are a genuine part of the organization/ enterprise.</div></div>firendzhttp://www.blogger.com/profile/15283816516424557590noreply@blogger.com0tag:blogger.com,1999:blog-4279471056317910162.post-90414456296761256902012-01-22T01:34:00.000-08:002012-01-22T01:34:05.034-08:00Range of Database Approach.<div dir="ltr" style="text-align: left;" trbidi="on"><br />
<div class="MsoNormal"><st1:place w:st="on"><st1:placetype w:st="on"><b><span style="font-size: 14.0pt; mso-bidi-font-size: 12.0pt;">Range</span></b></st1:placetype><b><span style="font-size: 14.0pt; mso-bidi-font-size: 12.0pt;"> of <st1:placename w:st="on">Database</st1:placename></span></b></st1:place><b><span style="font-size: 14.0pt; mso-bidi-font-size: 12.0pt;"> Approach.</span></b><span style="font-size: 14.0pt; mso-bidi-font-size: 12.0pt;"><o:p></o:p></span></div><div class="MsoNormal" style="line-height: 150%; text-align: justify;">In database approach the range of <b>database application</b> of from single user to multi user database . Generally we have seven database approaches. These are </div><div class="MsoNormal" style="line-height: 150%; text-align: justify;"><i><u>Personal Database approach:</u></i> Personal database approach is designed to support to store and to maintain the personal information. It can access by one user only. In general we can store personal database in personal computers like <i>laptops, cellular phones etc.</i> We have major problem with personal database approach that is <i>it does not allow sharing of the data</i> i.e. the personal database is working based on the <b>stand-alone </b>mode.</div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEghsHOYfoxqApfFqcLTFUSNxXxZOjqqdloS79NSCwGMdhAbsIdVOEtIODUtp6pTdnrqxzfCITHsTBFOHamSZDTBCcJcw9tZnNhjMocgSfS8m5xvOKdAxdAcg12f8ZNc_JTkTvphEfo6NmS1/s1600/appli.range.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEghsHOYfoxqApfFqcLTFUSNxXxZOjqqdloS79NSCwGMdhAbsIdVOEtIODUtp6pTdnrqxzfCITHsTBFOHamSZDTBCcJcw9tZnNhjMocgSfS8m5xvOKdAxdAcg12f8ZNc_JTkTvphEfo6NmS1/s1600/appli.range.jpg" /></a></div><div class="MsoNormal" style="line-height: 150%; text-align: justify;">Eg:</div><div class="MsoNormal" style="line-height: 150%; text-align: justify;"><i><u>Work group database approach:</u></i> In work group database approach , consists 20-25 members those team of people will develop a database of an organization . The work group database is designed to support to maintain database by a group of people.</div><div class="MsoNormal" style="line-height: 150%; text-align: justify;"> Work group database provides <b>data sharing</b> <b> .</b> In general work group database in <b>LAN</b> group network where database is available in one system this system is known as <b>database</b> <b>Server</b> .Database server is connected with 10 or more than 10 users .This type of architecture is known as one type of <b>client/server</b> architecture . Work group databases are sold to database vendors those vendors again sold to different customers and users.</div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhaparTl3iXC870Q4BewMRDYgzFUjLO_Z_4zT65hyphenhyphenmUVXGM2EKhHFMaKQhAKqH9uOP1S_GCEn_ns_IdIhddhGvo5mKZa1ISto_JU61fE9P4eGbAa4aD6c-XfQ_n7VP3_ZONJGqp1t9pOppl/s1600/images%255B9%255D.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhaparTl3iXC870Q4BewMRDYgzFUjLO_Z_4zT65hyphenhyphenmUVXGM2EKhHFMaKQhAKqH9uOP1S_GCEn_ns_IdIhddhGvo5mKZa1ISto_JU61fE9P4eGbAa4aD6c-XfQ_n7VP3_ZONJGqp1t9pOppl/s1600/images%255B9%255D.jpg" /></a></div><div class="MsoNormal" style="line-height: 150%; text-align: justify;">Eg.</div><div class="MsoNormal" style="line-height: 150%; text-align: justify;"><i><u>Departmental database approach:</u></i> Departmental database approach is designed to support to maintain departmental wise activities in an organization. It consist department information , procedures and functions.</div><div class="MsoNormal" style="line-height: 150%; text-align: justify;"> In departmental database consist 50-100 persons to perform a task. In an organization contain its department database server in an organization . The department database are connected to maintain from the main server to connect the database departmental database server , <b>distributed</b> the information to department and users . This technology is called as <b><i>two tier database architecture.</i></b></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhjsErE5_pISGLLKWHpKWdckq_q-6nPMonEnbHZK6Sp0XWVBRTBqG3vq-W1bNLQtymYRVZqKTtLFRArITy19JYikykIvbzgUiMIEhqWMEvmgfn4f0om5CEOmVSdjxoWhPYv8QmuNRbRQmgP/s1600/3tier.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhjsErE5_pISGLLKWHpKWdckq_q-6nPMonEnbHZK6Sp0XWVBRTBqG3vq-W1bNLQtymYRVZqKTtLFRArITy19JYikykIvbzgUiMIEhqWMEvmgfn4f0om5CEOmVSdjxoWhPYv8QmuNRbRQmgP/s1600/3tier.jpg" /></a></div><div class="MsoNormal" style="line-height: 150%; text-align: justify;">Eg:</div><div class="MsoNormal" style="line-height: 150%; text-align: justify;"><st1:city w:st="on"><i><u>Enterprise</u></i></st1:city><i><u> database approach:</u></i> <st1:place w:st="on"><st1:city w:st="on"><b>Enterprise</b></st1:city></st1:place><b> database </b> approach is designed to support to maintain organization database . It not only control the organizational database but also making decisions to support the database . It perform all the activities of an organization. The education of enterprise database approach two major departments these are </div><ol start="1" style="margin-top: 0in;" type="1"><li class="MsoNormal" style="line-height: 150%; mso-list: l0 level1 lfo1; tab-stops: list .5in; text-align: justify;"><st1:city w:st="on"><st1:place w:st="on">Enterprise</st1:place></st1:city> Resource Planning System (ERPS)</li>
<li class="MsoNormal" style="line-height: 150%; mso-list: l0 level1 lfo1; tab-stops: list .5in; text-align: justify;">Data warehousing .</li>
</ol><div class="MsoNormal" style="line-height: 150%; margin-left: .5in; text-align: justify;">ERPS is developed from <b>MRP</b>(Material Requirement Planning ) system .These system contains some functions such as how to distribute the data to entire organization and how to control the flow of data in an enterprise / organization .In an enterprise database we have entire organization database or information and historical information about the organization and collaboration organization information such enterprise database organization is known as data ware housing.</div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj6-QmSuR1AYbJwTlDvtOpX3j3zwDep2SC3yhGsMBF0JZK7438oYreIQDmvc-jlJCQBf6yywNHuur9ARavE6O10jBaIReVnytAvpkACaCKCGMJsfLChvw4w3LebP4pZG-LR3LqnC0eBT0P6/s1600/admin043.gif" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj6-QmSuR1AYbJwTlDvtOpX3j3zwDep2SC3yhGsMBF0JZK7438oYreIQDmvc-jlJCQBf6yywNHuur9ARavE6O10jBaIReVnytAvpkACaCKCGMJsfLChvw4w3LebP4pZG-LR3LqnC0eBT0P6/s1600/admin043.gif" /></a></div><div class="MsoNormal" style="line-height: 150%; margin-left: .5in; text-align: justify;">Eg:</div><div class="MsoNormal" style="line-height: 150%; text-align: justify;"><b><i>Internet</i></b><i>:</i> Using Internet protocols to establish connection and access company data or information by any person or user who may have or may not have relation with that organization is known as Internet.</div><div class="MsoNormal" style="line-height: 150%; text-align: justify;">Eg: To access data by external person or user who are related to other company is known as internet. i.e. Any student can access the data of certain University or Organization is called Internet process.</div><div class="MsoNormal" style="line-height: 150%; text-align: justify;"><b><i>Intranet:</i></b> Using Internet protocols to establish connection and access company data or information by limited persons or users who are related with that organization is known as Intranet.</div><div class="MsoNormal" style="line-height: 150%; text-align: justify;">Eg: To access data by staff and students etc who are related to the same company is known as intranet. i.e. Any student and staff can access the data of certain University or Organization is called Intranet process.</div><div class="MsoNormal" style="line-height: 150%; text-align: justify;"><b><i>Extranet:</i></b>Using Internet protocols to establish connection and access company data or information by company directors, customers, dealers and legal advisers etc who have a relation with that organization is known as Extranet.</div><div class="MsoNormal" style="line-height: 150%; text-align: justify;">Eg: In <st1:place w:st="on"><st1:city w:st="on">Hyderabad</st1:city></st1:place> .We have our University, Our college is in Nizamabad and Our college is affiliated or related to that University . Every University have their own database for maintaining the university </div><span style="font-size: 12pt;">Our college is connected with university database through <i>internet </i>in order to retrieve college rules and regulations this concept is known as Extranet.</span></div>firendzhttp://www.blogger.com/profile/15283816516424557590noreply@blogger.com0tag:blogger.com,1999:blog-4279471056317910162.post-22943553311552209322012-01-22T01:30:00.000-08:002012-01-22T01:30:17.216-08:00<div dir="ltr" style="text-align: left;" trbidi="on"><br />
<div class="MsoNormal"><b><u><span style="font-size: 14.0pt; mso-bidi-font-size: 12.0pt;">MAJOR COMPONENTS OF DATABASE ENVIRONMENT.<o:p></o:p></span></u></b></div><div class="MsoNormal"><br />
</div><div class="MsoNormal" style="line-height: 150%; text-align: justify;"><span style="font-size: 14.0pt; line-height: 150%; mso-bidi-font-size: 12.0pt;"> </span>Strong Database Environment consist of <b>9 (Nine) major components</b> to maintain the database successful. The Major components of database environment are </div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgZUZnlzUqrYkXkGhyphenhyphenMYX3XjY39mxPJakIGJ4NocR00yzcd-oKitxG5nke3e-aJEFkIOGvKCH2HyDuiaT3tX8-_irhmn7lw1sm-LwdxhWbyPM9aI6hzKGnaNlFY5Ze-AOWMbC_wcH6-Onte/s1600/dbms%255B1%255D.gif" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="270" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgZUZnlzUqrYkXkGhyphenhyphenMYX3XjY39mxPJakIGJ4NocR00yzcd-oKitxG5nke3e-aJEFkIOGvKCH2HyDuiaT3tX8-_irhmn7lw1sm-LwdxhWbyPM9aI6hzKGnaNlFY5Ze-AOWMbC_wcH6-Onte/s320/dbms%255B1%255D.gif" width="320" /></a></div><div class="MsoNormal" style="line-height: 150%; text-align: justify;"><br />
</div><div class="MsoNormal" style="line-height: 150%; text-align: justify;"><i><u>CASE Tools</u></i> : (Computer Aided Software Engineering Tools) .<b><i>CASE Tools are predefined tools</i></b>. These are <b><i>automatically designed the database</i></b> in database approach.</div><div class="MsoNormal" style="line-height: 150%; text-align: justify;"><i><u>Repository:</u></i> It is a <b><i>centralized location of data definitions, data relationships, reports, formats and other system components and descriptions of the data</i></b> is called Repository.</div><div class="MsoNormal" style="line-height: 150%; text-align: justify;"><i><u>DBMS:</u></i><u> </u>DBMS (Database Management System) : It is a Mechanism , <b><i>A system which is consist a set of well defined programs to create, store, Delete, manipulate and retrieve the data in an organization by using File Operations like create a file , update file, delete file and insert file efficiently</i></b> is known as DBMS.</div><div class="MsoNormal" style="line-height: 150%; text-align: justify;"><i><u>Database</u></i> A set of the interrelated data of an organization is a <b>database. </b>Usually it design to meet the information of multiple users in an organization .<b><i>The repository contains the definitions and structure of the data where as the database contain the occurrence of the data.<o:p></o:p></i></b></div><div class="MsoNormal" style="line-height: 150%; text-align: justify;"><i><u>Application Programs:</u></i> A <i>computer programs which is used to create and maintain the database to provide the information to users</i> is an <b>application programs</b>.</div><div class="MsoNormal" style="line-height: 150%; text-align: justify;"><i><u>User Interface:</u></i> <i>Languages, Menus, Commands and other facilities which are used to interact with the computers by user is</i> a user interface. Generally this component is work as a interface with each and every component in an database environment.</div><div class="MsoNormal" style="line-height: 150%; text-align: justify;"><i><u>Database Administrator: (DBA)</u></i>: DBA is a person who has a responsible for overall information resources and central control of an organization .</div><div class="MsoNormal" style="line-height: 150%; text-align: justify;"><i><u>System Developers:</u></i> These are persons such as system programmers and analysts , who designed new application programs is called system developers. </div><div class="MsoNormal" style="line-height: 150%; text-align: justify;"><i><u>End Users:</u></i> End user is a person who insert , delete and modify the data in the database and who request information from database is known as end user.</div></div>firendzhttp://www.blogger.com/profile/15283816516424557590noreply@blogger.com0tag:blogger.com,1999:blog-4279471056317910162.post-47502636165886275592012-01-21T05:17:00.000-08:002012-01-21T05:26:29.115-08:00COSTS & RISKS are involved in dbms<div dir="ltr" style="text-align: left;" trbidi="on"><br />
<h2>COSTS & RISKS involved in database development:<span style="font-size: 12pt; font-weight: normal;"><o:p></o:p></span></h2><div class="MsoNormal" style="line-height: 150%; text-align: justify;">In database approach in order to maintain or develop database we should take a risk and we should invest money , time and environment. Database approach when we develop a new database or when we maintain an existing database we should consider the following points.</div><div class="MsoNormal" style="line-height: 150%; text-align: justify;"><span style="font-family: Wingdings;">à</span> New specialized persons.</div><div class="MsoNormal" style="line-height: 150%; text-align: justify;"><span style="font-family: Wingdings;">à</span> Installation and manage cost and complexity.</div><div class="MsoNormal" style="line-height: 150%; text-align: justify;"><span style="font-family: Wingdings;">à</span> Conversion costs.</div><div class="MsoNormal" style="line-height: 150%; text-align: justify;"><span style="font-family: Wingdings;">à</span> Need for explicit back up and recovery.</div><div class="MsoNormal" style="line-height: 150%; text-align: justify;"><span style="font-family: Wingdings;">à</span> Organizational conflict.</div><div class="MsoNormal" style="line-height: 150%; text-align: justify;"><i><u>New specialized persons</u></i>: Organization adopted the database approach to maintain individuals to design and implement database for that an organization provides <b>DBA </b>and manage a staff of new people because <b>there is a rapid changes in the technology</b> .New people will have to be retrained or upgraded their knowledge in database approach in an organization required specialized skill persons to maintain the database.</div><div class="MsoNormal" style="line-height: 150%; text-align: justify;"><i><u>Installation and manage cost and complexity</u>:</i> A multi user database management system is a large and complex . It has a high level install cost requires a staff to trained persons to install and operate . It also require professionals to maintain annual maintenance and cost .These systems are <b>require <i>to install new software to upgrade the database for that we should take a risk to modify Hard ware and data communications in an organization.<o:p></o:p></i></b></div><div class="MsoNormal" style="line-height: 150%; text-align: justify;"><u style="font-style: italic;">..........................for </u> more details please visit www.database-concept.com</div></div>firendzhttp://www.blogger.com/profile/15283816516424557590noreply@blogger.com4tag:blogger.com,1999:blog-4279471056317910162.post-54208759128239407252012-01-19T09:03:00.001-08:002012-01-19T09:03:47.352-08:00DBA (DataBase Administrator)<div dir="ltr" style="text-align: left;" trbidi="on"><div class="MsoNormal" style="margin: 0in 0in 0pt;"><b style="mso-bidi-font-weight: normal;"><span style="font-size: 14pt; mso-bidi-font-size: 12.0pt;">DBA (Database Administrator)</span></b></div><div class="MsoNormal" style="margin: 0in 0in 0pt;"><br />
</div><div class="MsoNormal" style="line-height: 150%; margin: 0in 0in 0pt; text-align: justify;">One of the main reasons for using DBMS to having central control of both the data and the programs that access <span style="mso-spacerun: yes;"> </span>the data , the person who has such central control<span style="mso-spacerun: yes;"> </span>over the system is called the database administrator (DBA) . The functions of DBA<span style="mso-spacerun: yes;"> </span>as follows </div><div class="MsoNormal" style="line-height: 150%; margin: 0in 0in 0pt; text-align: justify;"><i style="mso-bidi-font-style: normal;"><u>Schema Definition</u><b style="mso-bidi-font-weight: normal;">:</b></i> The DBA creates the original <b style="mso-bidi-font-weight: normal;">database schema <span style="mso-spacerun: yes;"> </span></b><span style="mso-spacerun: yes;"> </span>by writing a set of Definitions that are translated by the <b style="mso-bidi-font-weight: normal;">compiler </b>to a set of tables that are stored in permanently in the <b style="mso-bidi-font-weight: normal;">data dictionary. </b></div><div class="MsoNormal" style="line-height: 150%; margin: 0in 0in 0pt; text-align: justify;"><i style="mso-bidi-font-style: normal;"><u>Storage structure and access method definition</u>:</i> The DBA creates appropriate storage structures to access methods by writing<span style="mso-spacerun: yes;"> </span>a set definitions by translated these are to data storage and <b style="mso-bidi-font-weight: normal;">data definition language</b> compiler.</div><div class="MsoNormal" style="line-height: 150%; margin: 0in 0in 0pt; text-align: justify;"><i style="mso-bidi-font-style: normal;"><u>Schema physical organization modification:</u></i> programmers accomplish the relatively rare modifications either to the data schema or to the description of the physical storage structure . Organization writing a set of definitions that are used either the <b style="mso-bidi-font-weight: normal;">DDL compiler</b> or the data storage and data definition language compiler to generate modifications to the appropriate internal system table.</div><div class="MsoNormal" style="line-height: 150%; margin: 0in 0in 0pt; text-align: justify;"><i style="mso-bidi-font-style: normal;"><u>Granting of authorization for data access:</u></i> The granting of different types of authorization allows the DBMS administrators to regulate which parts of the database various users can access the authorization<span style="mso-spacerun: yes;"> </span>information is kept in a separate structure that is consulted by<span style="mso-spacerun: yes;"> </span>the database systems when ever access to the user data is attempt in the system.</div><div class="MsoNormal" style="line-height: 150%; margin: 0in 0in 0pt; text-align: justify;"><i style="mso-bidi-font-style: normal;"><u><span style="mso-spacerun: yes;"> </span>Integrity constraints specification: </u></i>The <span style="mso-spacerun: yes;"> </span>data value stored in the database must satisfied certain consistency <b style="mso-bidi-font-weight: normal;">constraints </b>. The integrity constraints are must specify external system of DBA. These are kept in a special system structure that is consulted by database system when ever update in the<span style="mso-spacerun: yes;"> </span>system.</div><div class="MsoNormal" style="line-height: 150%; margin: 0in 0in 0pt; text-align: justify;"><b style="mso-bidi-font-weight: normal;"><i style="mso-bidi-font-style: normal;"><u>DBA Goals:</u></i></b></div><div class="MsoNormal" style="line-height: 150%; margin: 0in 0in 0pt; text-align: justify;">Protecting<span style="mso-spacerun: yes;"> </span>the database from unauthorized users and also to handle total data from the table<span style="mso-spacerun: yes;"> </span>in this way the DBA has two types of goals. These are</div><div class="MsoNormal" style="line-height: 150%; margin: 0in 0in 0pt; text-align: justify;"><i style="mso-bidi-font-style: normal;"><u>Integrity :</u></i> It is considered with making certain operations which are performed by the users or correct and maintain the data consistency in these ways the DBA should be maintained<span style="mso-spacerun: yes;"> </span>a <b style="mso-bidi-font-weight: normal;">key values</b> to the related table.</div><div class="MsoNormal" style="line-height: 150%; margin: 0in 0in 0pt; text-align: justify;"><i style="mso-bidi-font-style: normal;"><u><span style="mso-spacerun: yes;"> </span>Security:</u></i> It is considered with limiting users to performing only<span style="mso-spacerun: yes;"> </span>certain operations that are allowed the DBA should provide <b style="mso-bidi-font-weight: normal;">security </b>for data accessing from the database.</div></div>firendzhttp://www.blogger.com/profile/15283816516424557590noreply@blogger.com0tag:blogger.com,1999:blog-4279471056317910162.post-68328012549857880392012-01-19T09:02:00.000-08:002012-01-19T09:02:18.047-08:00DATA SHARING:<div dir="ltr" style="text-align: left;" trbidi="on"><div class="MsoNormal" style="margin: 0in 0in 0pt;"><b style="mso-bidi-font-weight: normal;"><i style="mso-bidi-font-style: normal;">DATA SHARING:</i><u> </u></b></div><div class="MsoNormal" style="line-height: 150%; margin: 0in 0in 0pt; text-align: justify;">The most significant<span style="mso-spacerun: yes;"> </span>difference between a file based systems and database systems is <b style="mso-bidi-font-weight: normal;"><i style="mso-bidi-font-style: normal;">Data sharing</i></b>. Data sharing also requires a major change in the way of data are handled and managed with in the organization.<span style="mso-spacerun: yes;"> </span>Data sharing are of 3 (three) types. They are </div><ol style="margin-top: 0in;" type="1"><li class="MsoNormal" style="line-height: 150%; margin: 0in 0in 0pt; mso-list: l1 level1 lfo1; tab-stops: list .5in; text-align: justify;">Sharing Data between functional units.</li>
<li class="MsoNormal" style="line-height: 150%; margin: 0in 0in 0pt; mso-list: l1 level1 lfo1; tab-stops: list .5in; text-align: justify;">Sharing data between management units.</li>
<li class="MsoNormal" style="line-height: 150%; margin: 0in 0in 0pt; mso-list: l1 level1 lfo1; tab-stops: list .5in; text-align: justify;">Sharing data between geographically dispersed location.</li>
</ol><ol style="margin-top: 0in;" type="1"><li class="MsoNormal" style="line-height: 150%; margin: 0in 0in 0pt; mso-list: l0 level1 lfo2; tab-stops: list .5in; text-align: justify;"><i style="mso-bidi-font-style: normal;"><u>Sharing data between functional units:</u></i> The term<span style="mso-spacerun: yes;"> </span>data sharing suggests that people in different functional areas are use a common pool of data. Each of these are own applications without data sharing the marketing group may have their data files. The purchasing group like accounts group their own data files and marketing group have their own data files and so on… each group benefits from its own data. <b style="mso-bidi-font-weight: normal;">Eg diagram.</b></li>
</ol><div class="MsoNormal" style="line-height: 150%; margin: 0in 0in 0pt 0.25in; text-align: justify;">In contrasts the effect of combining data into database is <b style="mso-bidi-font-weight: normal;">synergistic</b> that is the combined data are more valuable then the some of the data in separated files .Not only does each group continue to have access to its own data but with in a reasonable limits and control they have access to other data as well. In this environment the marketing department for eg: Is better of because it has access to data from purchasing, especially product evolution which provide valuable input for marketing campaigns.</div><ol start="2" style="margin-top: 0in;" type="1"><li class="MsoNormal" style="line-height: 150%; margin: 0in 0in 0pt; mso-list: l0 level1 lfo2; tab-stops: list .5in; text-align: justify;"><i style="mso-bidi-font-style: normal;"><u>Sharing data between Management units:</u></i> <b style="mso-bidi-font-weight: normal;">Diagram</b></li>
</ol><div class="MsoNormal" style="line-height: 150%; margin: 0in 0in 0pt 0.25in; text-align: justify;"><span style="mso-spacerun: yes;"> </span>Different levels of users also need to share data . The three different levels of users are 1. Operation level, 2. Middle Management Level, 3. Execute level.</div><div class="MsoNormal" style="line-height: 150%; margin: 0in 0in 0pt 0.25in; text-align: justify;">These three levels are corresponded to the three different types of system these are <i style="mso-bidi-font-style: normal;">Electronic data processing, Management information system, and<span style="mso-spacerun: yes;"> </span>Decision support system.</i></div><div class="MsoNormal" style="line-height: 150%; margin: 0in 0in 0pt 0.25in; text-align: justify;"><i style="mso-bidi-font-style: normal;">EXECUTIVE<span style="mso-spacerun: yes;"> </span></i><i style="mso-bidi-font-style: normal;"><span style="font-family: Wingdings; mso-ascii-font-family: "Times New Roman"; mso-char-type: symbol; mso-hansi-font-family: "Times New Roman"; mso-symbol-font-family: Wingdings;"><span style="mso-char-type: symbol; mso-symbol-font-family: Wingdings;">à</span></span> Decision Support System </i><i style="mso-bidi-font-style: normal;"><span style="font-family: Wingdings; mso-ascii-font-family: "Times New Roman"; mso-char-type: symbol; mso-hansi-font-family: "Times New Roman"; mso-symbol-font-family: Wingdings;"><span style="mso-char-type: symbol; mso-symbol-font-family: Wingdings;">à</span></span> Strategic Reports, Queries, Analysis.</i></div><div class="MsoNormal" style="line-height: 150%; margin: 0in 0in 0pt 0.25in; text-align: justify;"><i style="mso-bidi-font-style: normal;">MIDDLE MANAGEMENT </i><i style="mso-bidi-font-style: normal;"><span style="font-family: Wingdings; mso-ascii-font-family: "Times New Roman"; mso-char-type: symbol; mso-hansi-font-family: "Times New Roman"; mso-symbol-font-family: Wingdings;"><span style="mso-char-type: symbol; mso-symbol-font-family: Wingdings;">à</span></span> Management Information System </i><i style="mso-bidi-font-style: normal;"><span style="font-family: Wingdings; mso-ascii-font-family: "Times New Roman"; mso-char-type: symbol; mso-hansi-font-family: "Times New Roman"; mso-symbol-font-family: Wingdings;"><span style="mso-char-type: symbol; mso-symbol-font-family: Wingdings;">à</span></span> Management reports of functional areas.</i></div><div class="MsoNormal" style="line-height: 150%; margin: 0in 0in 0pt 0.25in; text-align: justify;"><i style="mso-bidi-font-style: normal;">Operations </i><i style="mso-bidi-font-style: normal;"><span style="font-family: Wingdings; mso-ascii-font-family: "Times New Roman"; mso-char-type: symbol; mso-hansi-font-family: "Times New Roman"; mso-symbol-font-family: Wingdings;"><span style="mso-char-type: symbol; mso-symbol-font-family: Wingdings;">à</span></span> Electronic Data Processing System<span style="mso-spacerun: yes;"> </span></i><i style="mso-bidi-font-style: normal;"><span style="font-family: Wingdings; mso-ascii-font-family: "Times New Roman"; mso-char-type: symbol; mso-hansi-font-family: "Times New Roman"; mso-symbol-font-family: Wingdings;"><span style="mso-char-type: symbol; mso-symbol-font-family: Wingdings;">à</span></span> Transaction file, Maintenance Processing and control reports.</i></div><div class="MsoNormal" style="line-height: 150%; margin: 0in 0in 0pt 0.25in; text-align: justify;">The relationships of<span style="mso-spacerun: yes;"> </span>the above three systems<span style="mso-spacerun: yes;"> </span>have to different management levels is shown in <b style="mso-bidi-font-weight: normal;">diagram .</b>These levels of users and system naturally requires three different types of data. The user at the operational level needs data for transaction processing that is include data for new accounts are changes to an existing accounts management. The management <b style="mso-bidi-font-weight: normal;">information system</b> level utilize summaries to indicate which sales representatives were most or least productive and executives at highest level used decision support system to discover long term trends that apply to their own corporation as well as to identify the economic social and political environment in which they operate. The <b style="mso-bidi-font-weight: normal;">DSS </b>means Decision Support System help them makes the decisions such as building a new factory starting or dropping a product line and DSS uses summery data from with in the company as well as market and author data form outside sources.</div><div class="MsoNormal" style="line-height: 150%; margin: 0in 0in 0pt 0.5in; mso-list: l0 level1 lfo2; tab-stops: list .25in; text-align: justify; text-indent: -27pt;"><span style="mso-list: Ignore;">3.</span><i style="mso-bidi-font-style: normal;"><u>Sharing data between geographically dispersed location:</u></i> A company<span style="mso-spacerun: yes;"> </span>with several </div><div class="MsoNormal" style="line-height: 150%; margin: 0in 0in 0pt 12pt; text-align: justify;">locations has important <b style="mso-bidi-font-weight: normal;">data distributed</b> over a valid geographically area sharing .<span style="mso-spacerun: yes;"> </span>these data is a significant<span style="mso-spacerun: yes;"> </span>problems. A centralized database is physically contained to a single location<span style="mso-spacerun: yes;"> </span>controlled by a single computer that is Personal computer<span style="mso-spacerun: yes;"> </span>most<span style="mso-spacerun: yes;"> </span>function for which databases are created and accomplished more easily . If the database is centralized and it is easily to update and back up , recovery and control access to a database . If we know database exactly where it is and what’s software control it and identify the remote place where it is located.</div></div>firendzhttp://www.blogger.com/profile/15283816516424557590noreply@blogger.com4tag:blogger.com,1999:blog-4279471056317910162.post-85612967696496602292012-01-17T09:34:00.000-08:002012-01-17T09:34:26.114-08:00European Public Policy Blog: Supporting research and innovation in Europe’s universities<a href="http://googlepolicyeurope.blogspot.com/2010/12/supporting-research-and-innovation-in.html#links">European Public Policy Blog: Supporting research and innovation in Europe’s universities</a><div>good post . do u know more database information please visit www.database-concept.com. in this the basic and unbelievable details are available .</div>firendzhttp://www.blogger.com/profile/15283816516424557590noreply@blogger.com0tag:blogger.com,1999:blog-4279471056317910162.post-34337620107932008992012-01-17T09:30:00.000-08:002012-01-17T09:30:44.833-08:00European Public Policy Blog: DatenDialog - Big Tent goes to Berlin<a href="http://googlepolicyeurope.blogspot.com/2011/11/datendialog-big-tent-goes-to-berlin.html">European Public Policy Blog: DatenDialog - Big Tent goes to Berlin</a>firendzhttp://www.blogger.com/profile/15283816516424557590noreply@blogger.com0tag:blogger.com,1999:blog-4279471056317910162.post-51632826428912721662012-01-17T02:13:00.000-08:002012-01-17T02:13:21.212-08:00database sharing<div dir="ltr" style="text-align: left;" trbidi="on"><br />
<div class="MsoNormal"><b><i>DATA SHARING:</i><u> <o:p></o:p></u></b></div><div class="MsoNormal" style="line-height: 150%; text-align: justify;">The most significant difference between a file based systems and database systems is <b><i>Data sharing</i></b>. Data sharing also requires a major change in the way of data are handled and managed with in the organization. Data sharing are of 3 (three) types. They are </div><ol start="1" style="margin-top: 0in;" type="1"><li class="MsoNormal" style="line-height: 150%; mso-list: l0 level1 lfo1; tab-stops: list .5in; text-align: justify;">Sharing Data between functional units.</li>
<li class="MsoNormal" style="line-height: 150%; mso-list: l0 level1 lfo1; tab-stops: list .5in; text-align: justify;">Sharing data between management units.</li>
<li class="MsoNormal" style="line-height: 150%; mso-list: l0 level1 lfo1; tab-stops: list .5in; text-align: justify;">Sharing data between geographically dispersed location.</li>
</ol><i><u><span style="font-size: 12pt;">Sharing data between functional units:</span></u></i><span style="font-size: 12pt;"> The term data sharing suggests that people in different functional areas are use a common pool of data.</span></div>firendzhttp://www.blogger.com/profile/15283816516424557590noreply@blogger.com0tag:blogger.com,1999:blog-4279471056317910162.post-60110193083329637902011-12-16T08:57:00.001-08:002011-12-16T08:57:07.191-08:00data abstraction<div dir="ltr" style="text-align: left;" trbidi="on"><div class="MsoNormal" style="line-height: 150%; margin: 0in 0in 0pt; text-align: justify;"><span style="font-family: Tahoma;">The standard database structure consisting of <i style="mso-bidi-font-style: normal;">conceptual , external and internal levels</i> . In three schema architecture have three levels of abstraction at which a database could be viewed. These three levels are .... for more details u may get please visit <a href="http://www.database-concept.com/">http://www.database-concept.com/</a></span></div></div>firendzhttp://www.blogger.com/profile/15283816516424557590noreply@blogger.com0tag:blogger.com,1999:blog-4279471056317910162.post-75832755658083977552011-12-16T08:52:00.000-08:002011-12-16T08:52:19.291-08:00DBMS Musings: Replication and the latency-consistency tradeoff<a href="http://dbmsmusings.blogspot.com/2011/12/replication-and-latency-consistency.html?spref=bl">DBMS Musings: Replication and the latency-consistency tradeoff</a>: As 24/7 availability becomes increasingly important for modern applications, database systems are frequently replicated in order to stay up ...firendzhttp://www.blogger.com/profile/15283816516424557590noreply@blogger.com0tag:blogger.com,1999:blog-4279471056317910162.post-5284096110437558382011-11-07T00:22:00.000-08:002011-11-07T00:24:53.127-08:00database models<div dir="ltr" style="text-align: left;" trbidi="on"><div class="MsoNormal" style="margin: 0in 0in 0pt;"><b style="mso-bidi-font-weight: normal;">DATA MODELS</b></div><div class="MsoNormal" style="line-height: 150%; margin: 0in 0in 0pt; text-align: justify;">Data model is a collection of logical constructs used to represented to data structure and data relationships found with in the databases . Database models can be grouped into two (2) categories. These are </div><ol style="margin-top: 0in;" type="1"><li class="MsoNormal" style="line-height: 150%; margin: 0in 0in 0pt; mso-list: l0 level1 lfo1; tab-stops: list .5in; text-align: justify;">Record based logical model<span style="mso-spacerun: yes;"> </span>(or) implementation model.</li>
<li class="MsoNormal" style="line-height: 150%; margin: 0in 0in 0pt; mso-list: l0 level1 lfo1; tab-stops: list .5in; text-align: justify;">Object based<span style="mso-spacerun: yes;"> </span>logical model (or) conceptual model.</li>
<li class="MsoNormal" style="line-height: 150%; margin: 0in 0in 0pt; mso-list: l0 level1 lfo1; tab-stops: list .5in; text-align: justify;">E-R (Entity – Relationship ) model.</li>
</ol><div class="MsoNormal" style="line-height: 150%; margin: 0in 0in 0pt 0.25in; text-align: justify;"><i style="mso-bidi-font-style: normal;"><u>Record based logical model / Implementation model:</u></i> This model emphases on how the data are represented in the database. It has 3 (three) types. These are </div><ol style="margin-top: 0in;" type="1"><li class="MsoNormal" style="line-height: 150%; margin: 0in 0in 0pt; mso-list: l1 level1 lfo2; tab-stops: list .5in; text-align: justify;">Hierarchical data model.</li>
<li class="MsoNormal" style="line-height: 150%; margin: 0in 0in 0pt; mso-list: l1 level1 lfo2; tab-stops: list .5in; text-align: justify;">Network data model.</li>
<li class="MsoNormal" style="line-height: 150%; margin: 0in 0in 0pt; mso-list: l1 level1 lfo2; tab-stops: list .5in; text-align: justify;">Relational data model.</li>
</ol><div class="MsoNormal" style="line-height: 150%; margin: 0in 0in 0pt 0.25in; text-align: justify;"><i style="mso-bidi-font-style: normal;"><u>Hierarchical data model </u></i><span style="mso-spacerun: yes;"> </span>we can represent the data as a tree model . The origin of data tree is the <b style="mso-bidi-font-weight: normal;">root</b> . The data is located at different level along a particular branch from the root is called<span style="mso-spacerun: yes;"> </span>is <b style="mso-bidi-font-weight: normal;">node</b> . the last node in the series is called <b style="mso-bidi-font-weight: normal;">leaf</b> . It supports one-to-many relationship.</div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgvyUDZ19z62USm72jcrT-W-pxEBJrIgEk0gqb12u0sN5lMum04ebC5c35vxg83j9W154D8V7wDoKvBHY-_8WIoQHrq_Xcw2wpvsy4ZobPi7wDYyxzgJVo2XVa-VHJ7z-0p8poo_YPincVE/s1600/heirarchical.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" ida="true" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgvyUDZ19z62USm72jcrT-W-pxEBJrIgEk0gqb12u0sN5lMum04ebC5c35vxg83j9W154D8V7wDoKvBHY-_8WIoQHrq_Xcw2wpvsy4ZobPi7wDYyxzgJVo2XVa-VHJ7z-0p8poo_YPincVE/s1600/heirarchical.jpg" /></a></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjmOa5mKCyVn4YPxs9Kvi7-naKarTaE0puTvLenSIk0sreUezE55NGl2FsOZobTQ8KYOLXL4BtaFxfjSraDDxw8JTJoSxvMWAPgQbTYDdubNzLHPyiiM27P0Kk6EZDWjEIH8LxfEKVqawy6/s1600/DatabaseDiagram.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="274" ida="true" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjmOa5mKCyVn4YPxs9Kvi7-naKarTaE0puTvLenSIk0sreUezE55NGl2FsOZobTQ8KYOLXL4BtaFxfjSraDDxw8JTJoSxvMWAPgQbTYDdubNzLHPyiiM27P0Kk6EZDWjEIH8LxfEKVqawy6/s320/DatabaseDiagram.jpg" width="320" /></a></div><div class="MsoNormal" style="line-height: 150%; margin: 0in 0in 0pt 0.25in; text-align: justify;"><span style="mso-spacerun: yes;"> </span><shapetype coordsize="21600,21600" filled="f" id="_x0000_t75" o:preferrelative="t" o:spt="75" path="m@4@5l@4@11@9@11@9@5xe" stroked="f"> <stroke joinstyle="miter"></stroke><formulas><f eqn="if lineDrawn pixelLineWidth 0"></f><f eqn="sum @0 1 0"></f><f eqn="sum 0 0 @1"></f><f eqn="prod @2 1 2"></f><f eqn="prod @3 21600 pixelWidth"></f><f eqn="prod @3 21600 pixelHeight"></f><f eqn="sum @0 0 1"></f><f eqn="prod @6 1 2"></f><f eqn="prod @7 21600 pixelWidth"></f><f eqn="sum @8 21600 0"></f><f eqn="prod @7 21600 pixelHeight"></f><f eqn="sum @10 21600 0"></f></formulas><path gradientshapeok="t" o:connecttype="rect" o:extrusionok="f"></path><lock aspectratio="t" v:ext="edit"></lock></shapetype><i style="mso-bidi-font-style: normal;"><u></u></i></div><div class="MsoNormal" style="line-height: 150%; margin: 0in 0in 0pt 0.25in; text-align: justify;"><span style="mso-spacerun: yes;"> </span>The main idea behind <i style="mso-bidi-font-style: normal;"><u>Network data model </u></i><span style="mso-spacerun: yes;"> </span>is to bring about <i style="mso-bidi-font-style: normal;">many-to many relationship</i> . This relationship between the different data items . These are called as sets. In this we use a pointer to locate a particular record </div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgVlEJeSoFTMyAiNBd9f05gOe-Mra5xT_VUQf5FWOaQ9-evkaAGOXVEGGHX4NDayVQ4oeXBM6_xC-THcUtl99kKZq2IKCQvaykUJjs2Wdl6fE4yF__dIL1x4LNoNmZVsR72QWtmWKKw8qvx/s1600/db+server.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" ida="true" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgVlEJeSoFTMyAiNBd9f05gOe-Mra5xT_VUQf5FWOaQ9-evkaAGOXVEGGHX4NDayVQ4oeXBM6_xC-THcUtl99kKZq2IKCQvaykUJjs2Wdl6fE4yF__dIL1x4LNoNmZVsR72QWtmWKKw8qvx/s1600/db+server.jpg" /></a></div><div class="MsoNormal" style="line-height: 150%; margin: 0in 0in 0pt 0.25in; text-align: justify;"><br />
</div><div class="MsoNormal" style="line-height: 150%; margin: 0in 0in 0pt 0.25in; text-align: justify;">The above diagram<span style="mso-spacerun: yes;"> </span>describes the vendor and item relationship should be represents in Network model in this it describes<span style="mso-spacerun: yes;"> </span>which vendor is selling a particular item.</div><div class="MsoNormal" style="line-height: 150%; margin: 0in 0in 0pt 0.25in; text-align: justify;">Dr.E.F.CODD first introduced the <i style="mso-bidi-font-style: normal;"><u>relational database data model</u></i> in 1970. this model allows<span style="mso-spacerun: yes;"> </span>the data to be represented in a simple row and column format, table. A system which consist database in the form of tables is <b style="mso-bidi-font-weight: normal;">RDBMS. </b></div><div class="MsoNormal" style="line-height: 150%; margin: 0in 0in 0pt; text-align: justify;"><span style="mso-spacerun: yes;"> </span>Each table indicating an entity , table consists rows and columns . Each column<span style="mso-spacerun: yes;"> </span></div><div class="MsoNormal" style="line-height: 150%; margin: 0in 0in 0pt; text-align: justify;"><span style="mso-spacerun: yes;"> </span>indicates record or data of entity and each column indicates attribute or field.</div><div class="MsoNormal" style="line-height: 150%; margin: 0in 0in 0pt 0.25in; text-align: justify;">Eg: </div><table border="1" cellpadding="0" cellspacing="0" class="MsoTableGrid" style="border-bottom: medium none; border-collapse: collapse; border-left: medium none; border-right: medium none; border-top: medium none; margin: auto auto auto 0.95in; mso-border-alt: solid windowtext .5pt; mso-border-insideh: .5pt solid windowtext; mso-border-insidev: .5pt solid windowtext; mso-padding-alt: 0in 5.4pt 0in 5.4pt; mso-yfti-tbllook: 480;"><tbody>
<tr style="mso-yfti-firstrow: yes; mso-yfti-irow: 0;"><td style="background-color: transparent; border-bottom: windowtext 1pt solid; border-left: windowtext 1pt solid; border-right: windowtext 1pt solid; border-top: windowtext 1pt solid; mso-border-alt: solid windowtext .5pt; padding-bottom: 0in; padding-left: 5.4pt; padding-right: 5.4pt; padding-top: 0in; width: 81pt;" valign="top" width="108"><div class="MsoNormal" style="line-height: 150%; margin: 0in 0in 0pt; text-align: justify;">Vendor No</div></td><td style="background-color: transparent; border-bottom: windowtext 1pt solid; border-left: #ece9d8; border-right: windowtext 1pt solid; border-top: windowtext 1pt solid; mso-border-alt: solid windowtext .5pt; mso-border-left-alt: solid windowtext .5pt; padding-bottom: 0in; padding-left: 5.4pt; padding-right: 5.4pt; padding-top: 0in; width: 1.25in;" valign="top" width="120"><div class="MsoNormal" style="line-height: 150%; margin: 0in 0in 0pt; text-align: justify;">Vendor Name</div></td><td style="background-color: transparent; border-bottom: windowtext 1pt solid; border-left: #ece9d8; border-right: windowtext 1pt solid; border-top: windowtext 1pt solid; mso-border-alt: solid windowtext .5pt; mso-border-left-alt: solid windowtext .5pt; padding-bottom: 0in; padding-left: 5.4pt; padding-right: 5.4pt; padding-top: 0in; width: 63pt;" valign="top" width="84"><div class="MsoNormal" style="line-height: 150%; margin: 0in 0in 0pt; text-align: justify;">Item</div></td></tr>
<tr style="mso-yfti-irow: 1;"><td style="background-color: transparent; border-bottom: windowtext 1pt solid; border-left: windowtext 1pt solid; border-right: windowtext 1pt solid; border-top: #ece9d8; mso-border-alt: solid windowtext .5pt; mso-border-top-alt: solid windowtext .5pt; padding-bottom: 0in; padding-left: 5.4pt; padding-right: 5.4pt; padding-top: 0in; width: 81pt;" valign="top" width="108"><div class="MsoNormal" style="line-height: 150%; margin: 0in 0in 0pt; text-align: justify;">111</div></td><td style="background-color: transparent; border-bottom: windowtext 1pt solid; border-left: #ece9d8; border-right: windowtext 1pt solid; border-top: #ece9d8; mso-border-alt: solid windowtext .5pt; mso-border-left-alt: solid windowtext .5pt; mso-border-top-alt: solid windowtext .5pt; padding-bottom: 0in; padding-left: 5.4pt; padding-right: 5.4pt; padding-top: 0in; width: 1.25in;" valign="top" width="120"><div class="MsoNormal" style="line-height: 150%; margin: 0in 0in 0pt; text-align: justify;">Ram</div></td><td style="background-color: transparent; border-bottom: windowtext 1pt solid; border-left: #ece9d8; border-right: windowtext 1pt solid; border-top: #ece9d8; mso-border-alt: solid windowtext .5pt; mso-border-left-alt: solid windowtext .5pt; mso-border-top-alt: solid windowtext .5pt; padding-bottom: 0in; padding-left: 5.4pt; padding-right: 5.4pt; padding-top: 0in; width: 63pt;" valign="top" width="84"><div class="MsoNormal" style="line-height: 150%; margin: 0in 0in 0pt; text-align: justify;">Mouse</div></td></tr>
<tr style="mso-yfti-irow: 2;"><td style="background-color: transparent; border-bottom: windowtext 1pt solid; border-left: windowtext 1pt solid; border-right: windowtext 1pt solid; border-top: #ece9d8; mso-border-alt: solid windowtext .5pt; mso-border-top-alt: solid windowtext .5pt; padding-bottom: 0in; padding-left: 5.4pt; padding-right: 5.4pt; padding-top: 0in; width: 81pt;" valign="top" width="108"><div class="MsoNormal" style="line-height: 150%; margin: 0in 0in 0pt; text-align: justify;">121</div></td><td style="background-color: transparent; border-bottom: windowtext 1pt solid; border-left: #ece9d8; border-right: windowtext 1pt solid; border-top: #ece9d8; mso-border-alt: solid windowtext .5pt; mso-border-left-alt: solid windowtext .5pt; mso-border-top-alt: solid windowtext .5pt; padding-bottom: 0in; padding-left: 5.4pt; padding-right: 5.4pt; padding-top: 0in; width: 1.25in;" valign="top" width="120"><div class="MsoNormal" style="line-height: 150%; margin: 0in 0in 0pt; text-align: justify;">Shyam</div></td><td style="background-color: transparent; border-bottom: windowtext 1pt solid; border-left: #ece9d8; border-right: windowtext 1pt solid; border-top: #ece9d8; mso-border-alt: solid windowtext .5pt; mso-border-left-alt: solid windowtext .5pt; mso-border-top-alt: solid windowtext .5pt; padding-bottom: 0in; padding-left: 5.4pt; padding-right: 5.4pt; padding-top: 0in; width: 63pt;" valign="top" width="84"><div class="MsoNormal" style="line-height: 150%; margin: 0in 0in 0pt; text-align: justify;">Keyboard</div></td></tr>
<tr style="mso-yfti-irow: 3; mso-yfti-lastrow: yes;"><td style="background-color: transparent; border-bottom: windowtext 1pt solid; border-left: windowtext 1pt solid; border-right: windowtext 1pt solid; border-top: #ece9d8; mso-border-alt: solid windowtext .5pt; mso-border-top-alt: solid windowtext .5pt; padding-bottom: 0in; padding-left: 5.4pt; padding-right: 5.4pt; padding-top: 0in; width: 81pt;" valign="top" width="108"><div class="MsoNormal" style="line-height: 150%; margin: 0in 0in 0pt; text-align: justify;">131</div></td><td style="background-color: transparent; border-bottom: windowtext 1pt solid; border-left: #ece9d8; border-right: windowtext 1pt solid; border-top: #ece9d8; mso-border-alt: solid windowtext .5pt; mso-border-left-alt: solid windowtext .5pt; mso-border-top-alt: solid windowtext .5pt; padding-bottom: 0in; padding-left: 5.4pt; padding-right: 5.4pt; padding-top: 0in; width: 1.25in;" valign="top" width="120"><div class="MsoNormal" style="line-height: 150%; margin: 0in 0in 0pt; text-align: justify;">Arun</div></td><td style="background-color: transparent; border-bottom: windowtext 1pt solid; border-left: #ece9d8; border-right: windowtext 1pt solid; border-top: #ece9d8; mso-border-alt: solid windowtext .5pt; mso-border-left-alt: solid windowtext .5pt; mso-border-top-alt: solid windowtext .5pt; padding-bottom: 0in; padding-left: 5.4pt; padding-right: 5.4pt; padding-top: 0in; width: 63pt;" valign="top" width="84"><div class="MsoNormal" style="line-height: 150%; margin: 0in 0in 0pt; text-align: justify;">Monitor</div></td></tr>
</tbody></table><br />
<div class="MsoNormal" style="line-height: 150%; margin: 0in 0in 0pt 0.25in; text-align: justify;"><i style="mso-bidi-font-style: normal;"><u>Conceptual Data model or Objective based logical model:</u></i> This model is consider with the represented in the database rather than how data is represented in an organization .It also included Entity Relationship model and uses this model in three types of relationships . These are </div><div class="MsoNormal" style="line-height: 150%; margin: 0in 0in 0pt 0.25in; text-align: justify;"><b style="mso-bidi-font-weight: normal;"><i style="mso-bidi-font-style: normal;">One-to-one Relationship</i></b>: This type of relationship mainly has to represent the relationship between two set values and these set values have a relationship between one set to another set values <span style="mso-spacerun: yes;"> </span>and specify the one-to-one relationship is shown as in the below. .Eg:</div><div class="MsoNormal" style="line-height: 150%; margin: 0in 0in 0pt 0.25in; text-align: justify;"><span style="mso-tab-count: 2;"> </span>Set A<span style="mso-tab-count: 2;"> </span>Set B</div><div class="MsoNormal" style="line-height: 150%; margin: 0in 0in 0pt 0.25in; text-align: justify;"><span style="mso-tab-count: 2;"> </span>1<span style="mso-spacerun: yes;"> </span><span style="mso-tab-count: 1;"> </span><span style="font-family: Wingdings; mso-ascii-font-family: "Times New Roman"; mso-char-type: symbol; mso-hansi-font-family: "Times New Roman"; mso-symbol-font-family: Wingdings;"><span style="mso-char-type: symbol; mso-symbol-font-family: Wingdings;">à</span></span> <span style="mso-tab-count: 1;"> </span>a</div><div class="MsoNormal" style="line-height: 150%; margin: 0in 0in 0pt 0.25in; text-align: justify;"><span style="mso-tab-count: 2;"> </span>3<span style="mso-tab-count: 1;"> </span><span style="font-family: Wingdings; mso-ascii-font-family: "Times New Roman"; mso-char-type: symbol; mso-hansi-font-family: "Times New Roman"; mso-symbol-font-family: Wingdings;"><span style="mso-char-type: symbol; mso-symbol-font-family: Wingdings;">à</span></span><span style="mso-tab-count: 1;"> </span>b</div><div class="MsoNormal" style="line-height: 150%; margin: 0in 0in 0pt 0.25in; text-align: justify;"><span style="mso-tab-count: 2;"> </span>9<span style="mso-tab-count: 1;"> </span><span style="font-family: Wingdings; mso-ascii-font-family: "Times New Roman"; mso-char-type: symbol; mso-hansi-font-family: "Times New Roman"; mso-symbol-font-family: Wingdings;"><span style="mso-char-type: symbol; mso-symbol-font-family: Wingdings;">à</span></span><span style="mso-tab-count: 1;"> </span>d<span style="mso-tab-count: 1;"> </span></div><div class="separator" style="clear: both; text-align: center;"><br />
</div><div class="MsoNormal" style="line-height: 150%; margin: 0in 0in 0pt 0.25in; text-align: justify;"><b style="mso-bidi-font-weight: normal;"><i style="mso-bidi-font-style: normal;">One-to-many Relationship:</i></b> <span style="mso-spacerun: yes;"> </span>This type of relationship mainly has to represent the relationship between two set values and<span style="mso-spacerun: yes;"> </span>the single value of one set should be participate in the relationship with another set of<span style="mso-spacerun: yes;"> </span>two different values and form One-to-many relationship . In this way <span style="mso-spacerun: yes;"> </span><span style="mso-spacerun: yes;"> </span>the second set of more than one values should be <span style="mso-spacerun: yes;"> </span>traced with single value of first set . Eg:</div><div class="MsoNormal" style="line-height: 150%; margin: 0in 0in 0pt 0.25in; text-align: justify;"> <a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjwc5X0wV-7RGGon_KDphKtwjS_sCoPhs5S1IU1PhC6SASfvjp-64pgIPFFvvzyKi_4u-zhyJTa6mTjacKoEPOwyekI0gIgf9Qou87_PrIcMce8xhQr98Eh2aO9tr4pp1Mp5dAKkhTuwIx8/s1600/geo.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" ida="true" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjwc5X0wV-7RGGon_KDphKtwjS_sCoPhs5S1IU1PhC6SASfvjp-64pgIPFFvvzyKi_4u-zhyJTa6mTjacKoEPOwyekI0gIgf9Qou87_PrIcMce8xhQr98Eh2aO9tr4pp1Mp5dAKkhTuwIx8/s1600/geo.jpg" /></a></div><div class="MsoNormal" style="line-height: 150%; margin: 0in 0in 0pt 0.25in; text-align: justify;"><br />
</div><div class="separator" style="clear: both; text-align: center;"><br />
</div><div class="MsoNormal" style="line-height: 150%; margin: 0in 0in 0pt 0.25in; text-align: justify;"><b style="mso-bidi-font-weight: normal;"><i style="mso-bidi-font-style: normal;">Many-to-Many Relationship:</i></b> These types of relationship mainly have to represent the relationship between two set values and the value of the first set <span style="mso-spacerun: yes;"> </span>should be participate in the relationship with more than single values of another set values and the same time<span style="mso-spacerun: yes;"> </span>the value of second set should be traced with more than one value and form a Many-to-Many Relationship. Eg:</div><div class="MsoNormal" style="line-height: 150%; margin: 0in 0in 0pt 0.25in; text-align: justify;"> <a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjl11Oo2YyIXhswpWrzTeDXaDOQfbJuUNMdywdaY172zSpZwOX3fu1xoTP1p4OOiyeCHAGAo9UYJJtSWEfiy64k1Ar5Vg_EKFKqga1c0d0jRyAoXelCmAyKGh3z8JXeyTpoplpz_cMQCkMd/s1600/appli.range.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" ida="true" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjl11Oo2YyIXhswpWrzTeDXaDOQfbJuUNMdywdaY172zSpZwOX3fu1xoTP1p4OOiyeCHAGAo9UYJJtSWEfiy64k1Ar5Vg_EKFKqga1c0d0jRyAoXelCmAyKGh3z8JXeyTpoplpz_cMQCkMd/s1600/appli.range.jpg" /></a></div><div class="MsoNormal" style="line-height: 150%; margin: 0in 0in 0pt 0.25in; text-align: justify;"><br />
</div><div class="MsoNormal" style="line-height: 150%; margin: 0in 0in 0pt 0.25in; text-align: justify;"><b style="mso-bidi-font-weight: normal;"><i style="mso-bidi-font-style: normal;">E-R Model (Entity-Relationship Model):</i></b> <b style="mso-bidi-font-weight: normal;">Entity</b> Relationship model consist of entities and specify the <b style="mso-bidi-font-weight: normal;">relationship</b> among one or more than one entities and form a Entity Relationship Model. Overall logical structure of a <b style="mso-bidi-font-weight: normal;">DBMS</b> can be expressed graphically by on <b style="mso-bidi-font-weight: normal;">E-R diagram</b> which consist the following <b style="mso-bidi-font-weight: normal;">components. Eg:</b></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhFzT_248tAYEGgKgrADonymrgxRkcTO6Sofz2jac6SHKoOnLJwN_jKDJSIJZ_OuL2UVawqAcTzUeVpbK-NtC12ug9_pA-3x36G3Yur-mH-0JxaUwF88-IvUdgxTU3lwbUO4pxIruSwNDiQ/s1600/simple_er%255B1%255D.gif" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="277" ida="true" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhFzT_248tAYEGgKgrADonymrgxRkcTO6Sofz2jac6SHKoOnLJwN_jKDJSIJZ_OuL2UVawqAcTzUeVpbK-NtC12ug9_pA-3x36G3Yur-mH-0JxaUwF88-IvUdgxTU3lwbUO4pxIruSwNDiQ/s320/simple_er%255B1%255D.gif" width="320" /></a>for more details u may get through please visit www.database-concept.com</div></div>firendzhttp://www.blogger.com/profile/15283816516424557590noreply@blogger.com0tag:blogger.com,1999:blog-4279471056317910162.post-29713452993857827942011-11-07T00:11:00.000-08:002011-11-07T00:11:35.001-08:00DATABASE ENVIRONMENT<div dir="ltr" style="text-align: left;" trbidi="on"><div class="MsoNormal" style="margin: 0in 0in 0pt;"><i style="mso-bidi-font-style: normal;"><span style="font-size: 16pt;">Database Environment</span></i><span style="font-size: 16pt;"> :</span></div><div class="MsoNormal" style="margin: 0in 0in 0pt;"><b style="mso-bidi-font-weight: normal;"><u>Introduction:</u></b></div><div class="MsoNormal" style="line-height: 150%; margin: 0in 0in 0pt; text-align: justify;"><a href="http://www.blogger.com/Database%20sys.doc">Database</a> is used to store, manipulate and retrieve data in every type of organization like Business, Healthcare, Education, Govt and Libraries. Database technology is used by Individuals like <a href="http://www.blogger.com/Range%20%20of%20Database%20Approach.doc">Personal Computers</a>, or by working groups Like Department wise, and <place w:st="on"><city w:st="on">Enterprise</city></place> wise and Distributed wise. </div><div class="MsoNormal" style="line-height: 150%; margin: 0in 0in 0pt; text-align: justify;">Many organizations are today building separate database these databases are called data warehouses<span style="mso-spacerun: yes;"> </span>. By using database we can develop relational database management, Online management System, and Employee Relationship management system. Etc. </div><div class="MsoNormal" style="line-height: 150%; margin: 0in 0in 0pt; text-align: justify;">By using database we can create or develop , retrieve and maintenance an organization data conveniently and successfully.</div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgR67YHvzGPsmxayUaZdMglqJpkuSdg_DbDPD1gQ3eHmnJIr0pjhC3XqhrnOwvbP3oNbgO1_qAPyJxph8ybCR-DSW84DQYpcr7jejUi5FclWm_qnQ0tsXhW_KO1zrm3jtUSvpy4wQwTA3m9/s1600/05-search-database-large.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="200" ida="true" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgR67YHvzGPsmxayUaZdMglqJpkuSdg_DbDPD1gQ3eHmnJIr0pjhC3XqhrnOwvbP3oNbgO1_qAPyJxph8ybCR-DSW84DQYpcr7jejUi5FclWm_qnQ0tsXhW_KO1zrm3jtUSvpy4wQwTA3m9/s320/05-search-database-large.jpg" width="320" /></a></div><div class="MsoNormal" style="line-height: 150%; margin: 0in 0in 0pt; text-align: justify;"><shapetype coordsize="21600,21600" filled="f" id="_x0000_t75" o:preferrelative="t" o:spt="75" path="m@4@5l@4@11@9@11@9@5xe" stroked="f"><stroke joinstyle="miter"></stroke><formulas><f eqn="if lineDrawn pixelLineWidth 0"></f><f eqn="sum @0 1 0"></f><f eqn="sum 0 0 @1"></f><f eqn="prod @2 1 2"></f><f eqn="prod @3 21600 pixelWidth"></f><f eqn="prod @3 21600 pixelHeight"></f><f eqn="sum @0 0 1"></f><f eqn="prod @6 1 2"></f><f eqn="prod @7 21600 pixelWidth"></f><f eqn="sum @8 21600 0"></f><f eqn="prod @7 21600 pixelHeight"></f><f eqn="sum @10 21600 0"></f></formulas><path gradientshapeok="t" o:connecttype="rect" o:extrusionok="f"></path><lock aspectratio="t" v:ext="edit"></lock></shapetype><shape alt="" id="_x0000_i1025" style="height: 135.75pt; width: 3in;" type="#_x0000_t75"><imagedata o:href="file:///C:\Documents%20and%20Settings\OM%20SAI%20%20RAM\My%20Documents\My%20Pictures\05-search-database-large.jpg" src="file:///C:\DOCUME~1\OMSAIR~1\LOCALS~1\Temp\msohtml1\01\clip_image001.jpg"></imagedata></shape></div><div class="MsoNormal" style="line-height: 150%; margin: 0in 0in 0pt; text-align: justify;">Data is a collection of raw facts . These facts may be in text, symbols, sounds, graphysics etc. data is the real thing of <span style="mso-spacerun: yes;"> </span>database of an organization.</div><div class="MsoNormal" style="line-height: 150%; margin: 0in 0in 0pt; text-align: justify;">Eg. ABC group of institutions. <place w:st="on"><city w:st="on">Hyderabad</city></place>.</div><div class="MsoNormal" style="line-height: 150%; margin: 0in 0in 0pt; text-align: justify;"><b style="mso-bidi-font-weight: normal;"><u><span style="font-size: 14pt; line-height: 150%;">Characteristics of DBMS:</span></u></b></div><div class="MsoNormal" style="line-height: 150%; margin: 0in 0in 0pt; text-align: justify;">DBMS is a mechanism to manage the designed database i.e. to create the data , insert the data, to update the data, and to delete the data in and from the database. </div><div class="MsoNormal" style="line-height: 150%; margin: 0in 0in 0pt; text-align: justify;">DBMS represents complex relationships between the data or information. </div><div class="MsoNormal" style="line-height: 150%; margin: 0in 0in 0pt; text-align: justify;">DBMS has a centralized data dictionary to store<span style="mso-spacerun: yes;"> </span>metadata .</div><div class="MsoNormal" style="line-height: 150%; margin: 0in 0in 0pt; text-align: justify;">DBMS keeps data control and redundancy i.e. avoid duplicate data.</div><div class="MsoNormal" style="line-height: 150%; margin: 0in 0in 0pt; text-align: justify;">DBMS has automatic intelligent backup and recovery procedures for its units. </div><div class="MsoNormal" style="line-height: 150%; margin: 0in 0in 0pt; text-align: justify;">DBMS provide different user interfaces to manipulate the data in the database.</div><div class="MsoNormal" style="line-height: 150%; margin: 0in 0in 0pt; text-align: justify;">Data Independency is a process the separation of data description from metadata<span style="mso-spacerun: yes;"> </span>i.e. in an organization data not depends on metadata. Each database should have database applications i.e. A large program<span style="mso-spacerun: yes;"> </span>or set of programs to perform a specified action is a n application .In database by using application we can<span style="mso-spacerun: yes;"> </span>read, write, update and delete of database information . An application which is used to perform database operations like read, write, update and delete is known as database application. When we develop our own database we should consider the legacy system or data. Legacy data means<span style="mso-spacerun: yes;"> </span>any data which is installed before developing our own database in the system is known as Legacy data. It contained by the system which is used prior to the installation of the system. When we develop a personnel database we should follow the database constraint. Constraint means when we develop our own database we should follow certain rules and conditions these rules and conditions are known as constrains.</div></div>firendzhttp://www.blogger.com/profile/15283816516424557590noreply@blogger.com0