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Management Information Systems, 10/e Raymond McLeod and George Schell © 2007 by Prentice Hall Management Information Systems, 10/e Raymond McLeod and George Schell 1 Chapter 6 Database Management Systems © 2007 by Prentice Hall Management Information Systems, 10/e Raymond McLeod and George Schell 2 Learning Objectives ► Understand the hierarchy of data. ► Understand database structures and how they work. ► Know how to relate tables together in a database. ► Recognize the difference between a database and a database management system. ► Understand the database concept. ► Know two basic methods for determining data needs. © 2007 by Prentice Hall Management Information Systems, 10/e Raymond McLeod and George Schell 3 Learning Objectives (Cont’d) ► Understand entity-relationship diagrams and class diagrams. ► Know the basics of reports and forms. ► Understand the basic difference between structured query language and query-by-example. ► Know about the important personnel who are associated with databases. ► Know the advantages and costs of database management systems. © 2007 by Prentice Hall Management Information Systems, 10/e Raymond McLeod and George Schell 4 Data Hierarchy ► Data field is the smallest unit of data. ► Record is a collection of related data fields. ► File is a collection of related records. ► Database is a collection of related files. General definition Restrictive definition © 2007 by Prentice Hall Management Information Systems, 10/e Raymond McLeod and George Schell 5 Database ► Table of rows & columns can be represented in a spreadsheet. ► Relational database structure is conceptually similar to a collection of related tables. ► Flat file is a table that does not have repeating columns; 1st normal form. ► Normalization is a formal process for eliminating redundant data fields which preserving the ability of the database to add, delete, and modify records without causing errors. © 2007 by Prentice Hall Management Information Systems, 10/e Raymond McLeod and George Schell 6 Figure 6.1 Spreadsheet as a Simple Database © 2007 by Prentice Hall Management Information Systems, 10/e Raymond McLeod and George Schell 7 Database (Cont’d) ► Key in a table is a field (or combination of fields) that contain a value that uniquely identifies each record in the table. ► Candidate key is a field that uniquely identifies each table row but is not the chosen key. ► Relating tables is done through sharing a common field & the value of the field determines which rows in the tables are logically joined. © 2007 by Prentice Hall Management Information Systems, 10/e Raymond McLeod and George Schell 8 Database Management System ► Database management system (DBMS) is a software application that stores the structure of the database, the data itself, relationships among data in the database, and forms & reports pertaining to the database. Self-describing set of related data. © 2007 by Prentice Hall Management Information Systems, 10/e Raymond McLeod and George Schell 9 Database Structures ► Hierarchical is formed by data groups, subgroups, and further subgroups; like branches on a tree. Worked well with TPSs. Utilized computer resources efficiently. ► Network allows retrieval of specific records; allows a given record to point to any other record in the database. © 2007 by Prentice Hall Management Information Systems, 10/e Raymond McLeod and George Schell 10 Figure 6.2 Hierarchical Structure © 2007 by Prentice Hall Management Information Systems, 10/e Raymond McLeod and George Schell 11 Database Structures (Cont’d) ► Relational is when the relationship between tables are implicit. ► Physical relationship is when the database structure (hierarchical, network) rely on storage addresses. ► Implicit relationship is when the database structure (relational) can be implied from the data. © 2007 by Prentice Hall Management Information Systems, 10/e Raymond McLeod and George Schell 12 A Relational Database Example ► A database named Schedule has been created from tables used earlier in the chapter and some others ► The database is implemented in Microsoft Access 2002 (also known as Access XP). ► Databases break information into multiple tables because if information were stored in a single table, many data field values would be duplicated. © 2007 by Prentice Hall Management Information Systems, 10/e Raymond McLeod and George Schell 13 Schedule Database ► The example is implemented on Microsoft Access DBMS but would be similar on any relational DBMS product. ► The COURSE table in Access (Figure 6.4) is a list of data field values. The table itself had to be defined in Access before values were entered into the data fields. ► Figure 6.5 shows the definition of the Code field. ► Figure 6.6 illustrates that Abbreviation field values will be looked up from a list of values in the DEPARTMENT table. ► Table 6.7 shows a single table of course and department fields before they were separated into different tables. © 2007 by Prentice Hall Management Information Systems, 10/e Raymond McLeod and George Schell 14 Figure 6.4 The COURSE Table © 2007 by Prentice Hall Management Information Systems, 10/e Raymond McLeod and George Schell 15 Figure 6.5 Defining the CODE Field © 2007 by Prentice Hall Management Information Systems, 10/e Raymond McLeod and George Schell 16 Figure 6.6 Look-up Values © 2007 by Prentice Hall Management Information Systems, 10/e Raymond McLeod and George Schell 17 Table 6.7 © 2007 by Prentice Hall Management Information Systems, 10/e Raymond McLeod and George Schell 18 Figure 6.7 Access View © 2007 by Prentice Hall Management Information Systems, 10/e Raymond McLeod and George Schell 19 Database Concept ► Database concept is the logical integration of records across multiple physical locations. ► Data independence is the ability to make changes in the data structure without making changes to the application programs that access the data. ► Data dictionary includes the definition of the data stored within the database & controlled by the database management system. © 2007 by Prentice Hall Management Information Systems, 10/e Raymond McLeod and George Schell 20 Creating a Database ► Determine data that needs to be collected & stored is a key step. ► Process-oriented approach Define the problem. Identify necessary decisions. Describe information needs. Determine the necessary processing. Specify data needs. © 2007 by Prentice Hall Management Information Systems, 10/e Raymond McLeod and George Schell 21 Determine Data Needs (Cont’d) ► Enterprise modeling approach takes a broad view of the firm’s data resources; all areas are considered, & synergy of data resources between business areas can be leveraged. Result: Enterprise data model © 2007 by Prentice Hall Management Information Systems, 10/e Raymond McLeod and George Schell 22 Figure 6.8 Enterprise Data Model © 2007 by Prentice Hall Management Information Systems, 10/e Raymond McLeod and George Schell 23 Data Modeling Techniques ► Entity-relationship diagrams (ERDs) is a graphical representation of data in entities and the relationships between entities. ► Entity is a conceptual collection of related data fields. ► Relationship is defined between entities. One-to-one – 1:1 One-to-many – 1:M Many-to-many – M:N © 2007 by Prentice Hall Management Information Systems, 10/e Raymond McLeod and George Schell 24 Figure 6.11 Entity-relationship Diagram © 2007 by Prentice Hall Management Information Systems, 10/e Raymond McLeod and George Schell 25 Diagramming Techniques (Cont’d) ► Class Diagram is a graphical representation of both the data used in an application and the actions associated with the data; object-oriented design model ► Objects are the data, actions taken on the data, & relationship between objects. ► Class diagrams consist of the named class, fields in the class, & actions (methods) that act upon the class. © 2007 by Prentice Hall Management Information Systems, 10/e Raymond McLeod and George Schell 26 Figure 6.13 Class Diagram © 2007 by Prentice Hall Management Information Systems, 10/e Raymond McLeod and George Schell 27 Using the Database ► Forms show 1 record at a time & can be used to add, delete, or modify database records. Navigation Accuracy Consistency Filtering subforms © 2007 by Prentice Hall Management Information Systems, 10/e Raymond McLeod and George Schell 28 Figure 6.15 Combined Data Entry Form © 2007 by Prentice Hall Management Information Systems, 10/e Raymond McLeod and George Schell 29 Using the Database (Cont’d) ► Reports are aggregated data from the database that are formatted in a manner that aids decision making. ► Queries is a request for the database to display selected records. ► Query-by-example (QBE) presents a standardized form that the user completes so the system can generate a true query. © 2007 by Prentice Hall Management Information Systems, 10/e Raymond McLeod and George Schell 30 Figure 6.16 Report of Departments © 2007 by Prentice Hall Management Information Systems, 10/e Raymond McLeod and George Schell 31 Structured Query Language ► Structured query language (SQL) is the code that RDBMSs use to perform their database tasks. ► Method of choice for interacting with webbased databases. ► Writing SQL statements are not difficult for most manager’s data needs. © 2007 by Prentice Hall Management Information Systems, 10/e Raymond McLeod and George Schell 32 Figure 6.20 SQL Code © 2007 by Prentice Hall Management Information Systems, 10/e Raymond McLeod and George Schell 33 Advanced Database Processing ► On-line analytical processing (OLAP) allows data analysis similar to statistical cross-tabulation. ► Data mining, data marts, & data warehousing focus on methodologies that offer users quick access to aggregated data specific to their decision-making needs. ► Knowledge discovery analyzes data usage & data commonality among different tables. © 2007 by Prentice Hall Management Information Systems, 10/e Raymond McLeod and George Schell 34 Database Personnel ► Database Administrator (DBA) is an expert in developing, providing, and securing databases; duties include Database Database Database Database © 2007 by Prentice Hall planning; implementation; operation; security. Management Information Systems, 10/e Raymond McLeod and George Schell 35 Database Personnel (Cont’d) ► Database programmer writes code to strip and/or aggregate data from the database High level of specialization & selection ► End user generates reports & forms, post queries to the database, & use results from their database inquiries to make decisions that affect the firm & its environmental constituents. © 2007 by Prentice Hall Management Information Systems, 10/e Raymond McLeod and George Schell 36 DBMSs in Perspective ► DBMS Advantages Reduce data redundancy. Achieve data independence. Retrieve data & information rapidly. Improve security. ► DBMS Disadvantages Obtain expensive software. Obtain a large hardware configuration. Hire and maintain a DBA staff. © 2007 by Prentice Hall Management Information Systems, 10/e Raymond McLeod and George Schell 37