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Mgt 20600: IT Management & Applications Databases Tuesday April 4, 2006.

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Presentation on theme: "Mgt 20600: IT Management & Applications Databases Tuesday April 4, 2006."— Presentation transcript:

1 Mgt 20600: IT Management & Applications Databases Tuesday April 4, 2006

2 Reminders  Reading –For today  Fundamentals text, Chapter Three, Organizing Data and Information –For next class on April 11 th  Fundamentals text, Chapter Six, Information and Decision Support Systems  Homework –Homework Four  Databases  Due Thursday, April 14th  Next week: Decision Support Systems

3 Databases  A well-designed and well-managed database is an extremely valuable tool in supporting decision making  Databases are key corporate assets  Databases are the foundation for sophisticated analyses that provide business intelligence –What new products to design –How to market to particular customer groups –Which customer groups are the most profitable

4 Traditional Approach to Data Management Traditional approach: separate data files are created for each application Results in data redundancy (duplication) Data redundancy conflicts with data integrity

5 Database Approach to Data Management Database approach: pool of related data is shared by multiple applications Significant advantages over traditional approach

6 Advantages of Database Approach  Improved strategic use of data  Reduced data redundancy  Improved data integrity  Easier modification and updating  Data and program independence  Better access to data and information  Standardization of data access  A framework for program development  Better overall protection of the data  Shared data and information resources

7 Disadvantages of the Database Approach  More complexity  More difficult to recover from a failure  More expensive

8 Databases  Databases must contain –Accurate information –Right kinds of information –Current information –Information from all organizational functions

9 Database Data  Data regarding –Important entities  Customers  Suppliers  Transactions –Each entity will have a number of attributes about which you want to collect and store information  Customer address  Customer phone number  Customer account number

10 Entities, Attributes, Keys Entity: a generalized class of people, places, or things (objects) for which data is collected, stored, and maintained (Table and records) Attribute: a characteristic of an entity (fields) Data item: a value of an attribute (fields) Key: field(s) that identify a record Primary key: field(s) that uniquely identify a record

11 Hierarchy of Data Field: name, number, or characters that describe an aspect of a business object or activity Record: a collection of related data fields File: a collection of related records Database: a collection of integrated and related files

12 Data Modeling and the Relational Database Model  When building a database, consider: –Content: What data should be collected, at what cost? –Access: What data should be provided to which users, and when? –Logical structure: How should data be arranged to make sense to a given user? –Physical organization: Where should data be physically located?

13 Data Modeling  Building a database requires two types of design –Logical design  Shows an abstract model of how data should be structured and arranged to meet an organization’s information needs –Physical design  Fine-tunes the logical database design for performance and cost considerations

14 Data Modeling  Data model: a diagram of data entities and their relationships  Entity-relationship (ER) diagrams: data models that use basic graphical symbols to show the organization of and relationships between data

15 Data Modeling An Entity-Relationship (ER) Diagram for a Customer Order Database

16 The Relational Database Model  Relational model: all data elements are placed in two-dimensional tables (relations), which are the logical equivalent of files  In the relational model: –Each table represents a data entity –Each row of a table represents a specific instance of a data entity –Columns of the table represent attributes

17 The Relational Database Model A Relational Database Model

18 Creating and Modifying the Database  Data definition language (DDL) –Collection of instructions/commands that define and describe data and data relationships in a database –Allows database creator to describe the data and the data relationships that are to be contained in the schema and the subschemas  Data dictionary: a detailed description of all the data used in the database

19 Storing and Retrieving Data Logical and Physical Access Paths

20 Providing a User View  Schema: description of the entire database  User view: user-accessible portion of the database  Subschema –Contains a description of a subset of the database –Identifies which users can view and modify the data items in the subset –Is used to create different user views

21 Providing a User View The Use of Schemas and Subschemas

22 Creating and Modifying the Database A Typical Data Dictionary Entry

23 Manipulating Data and Generating Reports  Data manipulation language (DML): commands that manipulate the data in a database –Query-By-Example (QBE): a visual approach to developing database queries or requests –Structured Query Language (SQL): ANSI standard query language for relational databases –Database programs can produce reports, documents, and other outputs

24 Manipulating Data  Selecting: eliminates rows according to criteria  Projecting: eliminates columns in a table  Joining: combines two or more tables  Linking: relates or links two or more tables using common data attributes

25 Manipulating Data Linking Data Tables to Answer an Inquiry

26 Database Administration  Database administrator (DBA): directs or performs all activities to maintain a database environment –Designing, implementing, and maintaining the database system and the DBMS –Establishing policies and procedures –Training employees

27 Selecting a Database Management System  Important characteristics of databases to consider: –Size of the database –Number of concurrent users –Performance –Ability to be integrated with other systems –Features of the DBMS –Vendor considerations –Cost of the system

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