Technology Guide 3 Data and Database T3-1

IT for Management Prof. Efraim Turban T3-2 File Management Hierarchy of data for a computer-based file Record Field Byte Bit Record Field Byte Bit File Database File

IT for Management Prof. Efraim Turban T3-3 File Management Entity –a person, place, thing, or event on which we maintain information Attribute –characteristic or quality describing a particular entity –corresponds to a field Key Field –a file that uniquely identifies that record –an identified filed

IT for Management Prof. Efraim Turban T3-4 Accessing Records from Computer Files Sequential File Organization –data records must be retrieved in the same physical sequence in which they are stored –magnetic tape Direct or Random File Organization –Users can access records in an sequence, without regard to actual physical order on the storage medium –magnetic disks

IT for Management Prof. Efraim Turban T3-5 Problems Arising from the Environment Data Redundancy : the same piece of information could be duplicated in several files Data Inconsistency : the actual values across various copies of the data no longer agree Data Isolation : data files are organized differently, stored in different formats, and often physically inaccessible to other applications Security : new application may be added to the system on an ad hoc basis Data Integrity : data values must often meet integrity constraints Application/Data Independence : application should not have to be developed with regard to how the data are stored

IT for Management Prof. Efraim Turban T3-6 Database and Database Management Systems Database –an organized logical grouping of related files –no data redundancy, data isolation, and data inconsistency Database Management Systems (DBMS) –a program that provides access to a database –permits an organization to centralize data, manage them efficiently, and provide access to the stored data by application programs

IT for Management Prof. Efraim Turban T3-7 Specialized Database Geographical Information Database –contains locational data for overlaying on maps or images Knowledge Database –stores decision rules used to evaluate situations and helps users make decisions like an expert Multimedia Database –Stores data on many media – sounds, video, images, graphic animation, and text

IT for Management Prof. Efraim Turban T3-8 Data Definition Language (DDL) Schema –the logical description of the entire database and the listing of all the data items and the relationships among them Subschema –the specific set of data from the database that is required by each application

IT for Management Prof. Efraim Turban T3-9 Data Manipulation language (DML) Structured Query Language (SQL) –combines both DML and DDL features –offers the ability to perform complicated searches with relatively simple statements Query-by-example (QBE) –allows users to select a table and chooses the fields to be included in the answer as the example he provided

IT for Management Prof. Efraim Turban T3-10 Data Dictionary Data dictionary is a file that stores definitions of data elements and data characteristics such as usage, physical representation, ownership, authorization, and security

IT for Management Prof. Efraim Turban T3-11 Hierarchical Database Model It relates data by rigidly structuring data into an inverted “tree” A single root or master field (Key) –identifies the type location, or ordering of the records A variable number of subordinate fields –defines the rest of the data within a record

IT for Management Prof. Efraim Turban T3-12 Network Database Model It creates relationships among data through a linked-list structure in which subordinated records can be linked to more than one parent Pointers –link subordinates and parents –storage addresses that contain the location of the related record

IT for Management Prof. Efraim Turban T3-13 Relational Database Model It is based on the simple concept of tables in order to capitalize on characteristics of rows and columns of data, which is consistent with real-world business situations Relations : table Record : row of data Field : column of data Object-relational Database Systems

IT for Management Prof. Efraim Turban T3-14 Creating Database Conceptual Design –an abstract model of the database from the user or business perspective –Describes how the data elements in the database are to be grouped Physical Design –shows how the database is actually arranges on direct access storage devices

IT for Management Prof. Efraim Turban T3-15 Entity-relationship Modeling Entity is something that can be identified in the users’ work environment Instance of an entity is the representation of a particular entity Attributes describe the entity’s characteristics Identifiers are attributes that identify entity instances Relationships can include many entities

IT for Management Prof. Efraim Turban T3-16 Entity-Relationship Diagram Table Class Student Professor Name ID Number Major Departmet Class Taught Name Attribute EntityRelationship 1:N One to many

IT for Management Prof. Efraim Turban T3-17 Normalization of Relational Databases Functional Dependency –a relationship between or among attributes, where, given the value of one attribute, we can obtain the value of another attribute

IT for Management Prof. Efraim Turban T3-18 Emerging Database Models Multimedia Database : an additional database that enables end users to quickly retrieve and present completes data that involve many dimensions Deductive Databases Object-oriented Database : used for OO programming Multimedia and Hypermedia Database : analogous to textual and numeric data

IT for Management Prof. Efraim Turban T3-19 Data Warehouses It is an additional database that is designed to support DSS, EIS, online analytical process (OLAP), and other end-user activities. It can provide an “executive view” of data and a unified corporate picture to the end- users by combining the data from many operational systems and incompatible databases without affecting the performance of the running operational systems

IT for Management Prof. Efraim Turban T3-20 Database Topology Centralized Database has all the related files in one physical location Distributed Database has complete copies of a database, or portions of a database, in more than one locations Replicated Database has complete copies of the entire database in several locations Partitioned Database is subdivided, so that each location has a portion of the entire database

IT for Management Prof. Efraim Turban T3-21 Physical vs. Logical Data View Physical View –deals with the actual, physical arrangement and location of data in the direct access storage devices (DASD) Logical View –represents data in a format that is meaningful to a user and to the software programs that process that data

IT for Management Prof. Efraim Turban T3-22 Database Management Database Design Database Implementation Database Administrators –responsible for ensuring that the database fulfills that user’s business needs, in terms of functionality s well for the data itself

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