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Database management Systems �A database management system (DBMS), or database program, is software application that permits you come create, access, and manage a database. �DBMSs are accessible for numerous sizes and species of computers.




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Database management Systems


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Data dictionary �A data dictionary, sometimes referred to as a repository, includes data around each ar in those files. �For each paper it shop details such together the record name, description, the file’s relationship to various other files, and the number of records in the file. �For every field, it stores the ar name, description, field type, ar size, default value, validation rules, and also the field’s connection to various other fields.


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Data thesaurus �Because the data dictionary contains details about data, some speak to it metadata, meta definition more comprehensive. �It is a crucial backbone come a DBMS therefore only expert professionals must update that is contents. �It is provided to perform validation checks and limit the type of data that can be entered.


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Data dictionary �A data dictionary permits users to specify a default value for a field, i m sorry is a value that the DBMS initially display screens in a field. ◦ Ex. If most students live in Indiana, the default value might read ‘IN’. �The user doesn’t have to kind the default value which help in to reduce errors.


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Data dictionary


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File Retrieval and Maintenance �A DBMS offers several tools that allow users and also programs to retrieve and maintain data in the database (adding, modifying, and also deleting). �To retrieve or pick data in a database, girlfriend query it, which is a request for details data native the database. �Users deserve to instruct the DBMS come display, print, or keep the results of a query, make it one of the an ext powerful database features.


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Query Language �A query language is composed of simple, English-like explanation that allow users to specify the data to display, print, or store. �Each has actually its own grammar and vocabulary. �A human being without programming experience can learn a query language in a brief time. �Most queries are offered to retrieve data. �Some DBMSs provide wizards to overview


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Query by example �Most DBMSs encompass query by instance (QBE), a feature that has a graphical user user interface to aid users v retrieving data.


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Form �A form, sometimes referred to as a data entry form, is a home window on the display that provides locations for start or editing data in a database. �Well-designed creates should validate data together it is entered. �A type that sends gotten in data throughout a network or the web is called an eform, short for digital form. �E-forms normally use a way to for sure the data while that is transported throughout the network.


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Form


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Report Generator �A report generator, additionally called a report writer, permits users to style a report on the screen, retrieve data right into the report design, and then display or print the report. �Unlike a form, report generators can only retrieve data. �Report generators allow you to style the page and some allow you to create a report together a net page.


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Report Generator


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Data protection �A DBMS provides way to ensure that only authorized users can access data at permitted times. �Most DBMSs enable different level of access privileges to be identified for each field in the database, defining the actions that a details user or group can perform.


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Data security �Access privileges for data involve establishing who can enter brand-new data, change existing data, delete unwanted data, and also view data. ◦ Ex. A college student would have actually read-only privileges: enabling them to see the perform of readily available classes but not adjust them. ◦ Ex. A room head would be able to modify the data. ◦ Ex. Various other users would have actually no access privileges come the data.


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Data security �Many organizations adopt a principle of least privilege policy, whereby users’ access privileges are limited to the shortest level crucial to perform required tasks.


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Backup and Recovery �Occasionally a database is damaged or destroyed, so a DBMS offers a range of techniques to restore the database come a usable form. �A backup, or copy, the the entire database need to be made on a continuous basis. �Some DBMSs have a built-in backup utility while others need a different utility.


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Backup and also Recovery �More facility DBMSs maintain a log, which is a listing of tasks that change the materials of the database. ◦ Ex. A registration clerk modifies a student’s address, the adjust will show up in the log. �The log in contains: ◦ A copy of the record prior to the readjust called the before image ◦ The readjust being make ◦ and also a copy that the document after the readjust called the after image ◦ The log in may additionally store that made the readjust and when.


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Backup and also Recovery �DBMSs that produce logs usually provide a recovery unit, which supplies the logs and/or backups to regain a database when it i do not care damaged or ruined using rollforward and also rollback techniques. �In a rollforward, or forward recovery, the DBMS offers the log to reenter transforms made to the database due to the fact that the last save or backup. �In a rollback, or behind recovery, the DBMS offers the log in to undo any changes made to the database during a details


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Backup and also Recovery �Continuous back-up is a backup setup in which all data is backed up whenever a change is made. �Continuous backup provides restore in a issue of seconds. �This method can cost more but is cultivation in popularity because of its benefits.


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Relational, Object-Oriented, and also Multidimensional Databases �Every database and also DBMS is based upon a details data model. �A data model is composed of rules and standards that define how the database organizes data.


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Relational, Object-Oriented, and also Multidimensional Databases �Three renowned data models in usage today are relational, object-oriented, and multidimensional. �Some are dubbed object-relational databases since they integrate features of the relational and also objectoriented data models.


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Relational Databases �A relational database is a database the stores data in tables the consist the rows and columns. �Each row has actually a primary crucial and each column has actually a unique name. �A developer that a relational database refers to a file as a relation, a record as a tuple, and also a field as an attribute.


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Relational Databases �A user the a relational database refers to a document as a table, a record as a row, and also a field as a column. �In enhancement to save data, a relational database likewise stores data relationships, i m sorry are links within the data. �With a relational database, girlfriend can collection up a relationship between tables with typical fields.


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Relational Databases


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Relational Databases �A developer that relational databases supplies normalization to organize the data in the database. �Normalization is a procedure designed to ensure the data in ~ the relations (tables) includes the the very least amount of duplication.


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SQL �Structured query Language (SQL) is a popular query language that enables users to manage, update, and also retrieve data. �SQL has special keywords and rules that users include in SQL statements.


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Object-Oriented Databases �An object-oriented database (OODB) stores data in objects. �An object is an object that includes data, and the plot that check out or process the data. �OODBs have the right to store much more types of data 보다 relational databases, access data faster, and allow programmers to reuse objects.


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Object-Oriented Databases �A multimedia database shop images, audio clips, and/or video clip clips. ◦ Ex. Voice mail mechanism �A groupware database stores files such as schedules, calendars, manuals, memos, and reports. ◦ Ex. Schedules for meeting times.


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Object-Oriented Databases �A computer-aided architecture (CAD) database stores data around engineering, architectural, and scientific designs. ◦ includes a perform of materials of the item being designed, the relationship amongst components, and also design drafts. �A hypertext database consists of text web links to other varieties of documents. �A hypermedia database has text, graphics, video, and also sound.


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Object questions Language �Object-oriented and object-relational databases often use a query language referred to as object query language (OQL) to manipulate and retrieve data. �OQL is similar to SQL and also uses countless of the exact same rules, grammar, and keywords.


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Multidimensional Databases �A multidimensional database shop data in dimensions. �Whereas a relational database is a two-dimensional table, a multidimensional database deserve to store much more than two dimensions that data. �These multiple dimensions, well-known as hypercube, allow users to accessibility and analyze any type of view the the database data.


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Multidimensional Databases �The variety of dimensions varies. ◦ Ex. A retail company might have actually 4: products, customers, regions, and time. �Nearly every multidimensional database has a measurement of time. �Multidimensional databases have the right to consolidate data much faster than a relational database.


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Data Warehouses �One applications that supplies multidimensional databases is a data warehouse, which is a huge database that stores and also manages the data compelled to analyze historical and also current transactions. �A data warehouse commonly has a userfriendly user interface so users can easily interact with that data.


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Data Warehouses �Data in a spread database exist in plenty of separate areas through a network or the Internet and is available through a single server. �Data warehouses frequently use a procedure called data mining to find patterns and relationships amongst data. ◦ Ex. E-commerce because that customer preferences �A smaller sized version that a data warehouse, a data mart, has a database the helps a details group or department make decisions.


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Web Databases �Much that the information on the web exists in databases save on the Web. �Some net databases are collaborative databases, where customers store and share photos, videos, recordings, and also other personal media with registered users. �The net page is offered as the front finish to the database.


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Web Database �A internet database usually lives on a database server, i beg your pardon is a computer that stores and also provides access to a database. �One kind of routine that manages the sending and receiving that data in between the former end and also the database server is a CGI (Common Gateway Interface) script.


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Database management �Managing a company’s database requires a good deal of coordination. �The duty of coordinating the use of the database belongs to the database experts and administrators.


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Database style Guidelines �A closely designed database renders it simpler for a user come query the database, modify its data, and create reports. ◦ recognize the function of the database ◦ architecture the tables or documents ◦ style the records and also fields because that each table ◦ identify the relationship among the tables




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Role of the Database analysts and Administrators �The database analyst (DA), or data modeler, concentrates on the meaning and usage of data. �The DA decides top top the suitable placement that fields, defines the relationships amongst data, and identifies users’ access privileges. �The database administrator (DBA) requires a an ext technical inside view of the data. �The DBA creates and maintains the data dictionary, manages defense of the database, monitors the performance of the database, and also checks backup and recovery procedures.


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Role of the Employee as a User �Today, employees accessibility databases from their office desktop computers, notebook computers, or also smart phones and other mobile devices. �Employees interact with databases related to inventory and also identify brand-new data in the database.