MANAGEMENT INFORMATION SYSTEM

Chapter 6Database Management Systems

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OVERVIEW

Spreadsheet as a simple DatabaseTables Database StructureTypes of DatabasesRelational DatabasesIntroduction to Microsoft AccessCreating Table Using Microsoft

AccessMicrosoft Access ObjectsQuery, Form, Reports

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THE 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

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DATABASE Table of rows and 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 while preserving the ability of the database to add, delete, and modify records without causing errors.

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SPREADSHEET EXAMPLE OF COURSE TABLE

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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 and the value of the field determines which rows in the tables are logically joined.

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DATABASE STRUCTURES

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 and reports pertaining to the database.

Self-describing set of related data.

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HIERARCHICAL 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.

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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.

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A RELATIONAL DATABASE EXAMPLE

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.

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THE 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.

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FIGURE 6.4 THE COURSE TABLE IN ACCESS

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FIGURE 6.5 DEFINING THE CODE FIELD

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FIGURE 6.6 LOOK-UP VALUES

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UN-SEPERATED TABLE OF COURSE AND DEPARTMENT DATA FIELDS

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FIGURE 6.7 ACCESS VIEW OF TABLES, FIELDS, AND THEIR RELATIONSHIPS

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THE 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 and controlled by the database management system.

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CREATING A DATABASE

Determine data that needs to be collected and stored is a key step.

Process-oriented approach Define the problem. Identify necessary decisions. Describe information needs. Determine the necessary processing. Specify data needs.

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DETERMINE DATA NEEDS

Enterprise modeling approach takes a broad view of the firm’s data resources; all areas are considered, and synergy of data resources between business areas can be leveraged. Result: Enterprise data model

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FIGURE 6.8 CREATING AN ENTERPRISE DATA MODEL

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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

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FIGURE 6.11 ENTITY-RELATIONSHIP DIAGRAM

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DIAGRAMMING TECHNIQUES

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, and relationship between objects.

Class diagrams consist of the named class, fields in the class, and actions (methods) that act upon the class.

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FIGURE 6.13 CLASS DIAGRAM

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USING THE DATABASE

Forms show one record at a time and can be used to add, delete, or modify database records. Navigation Accuracy Consistency Filtering Subforms

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FIGURE 6.15 COMBINED DATA ENTRY FORM FOR THE COURSE AND PROJECT TABLES

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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.

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FIGURE 6.16 REPORT OF DEPARTMENTS SHOWING COURSES OFFERED AND COURSE PROJECTS

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STRUCTURED QUERY LANGUAGE

Structured query language (SQL) is the code that RDBMSs use to perform their database tasks. Method of choice for interacting with Web-based

databases. Writing SQL statements are not difficult for most

manager’s data needs.

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FIGURE 6.20 STRUCTURED QUERY LANGUAGE CODE TO FIND PROJECTS FOR THE MIS105 COURSE

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DATABASE PERSONNEL

Database Administrator (DBA) is an expert in developing, providing, and securing databases; duties include: Database planning; Database implementation; Database operation; Database security.

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DATABASE PERSONNEL (CONT’D)

Database programmer writes code to strip and/or aggregate data from the database High level of specialization and selection

End user generates reports and forms, post queries to the database, and use results from their database inquiries to make decisions that affect the firm and its environmental constituents.

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DBMSS IN PERSPECTIVE

DBMS Advantages Reduce data redundancy. Achieve data independence. Retrieve data and information rapidly. Improve security.

DBMS Disadvantages Obtain expensive software. Obtain a large hardware configuration. Hire and maintain a DBA staff.