1 Management Information Systems M Agung Ali Fikri, SE. MM.

2 Chapter 6 Database Management Systems

3 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.

4 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.

5 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

6 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; 1 st 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.

7 Figure 6.1 Spreadsheet as a Simple Database

8 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.

9 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.

10 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.

11 Figure 6.2 Hierarchical Structure

12 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.

13 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.

14 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.

15 Figure 6.4 The COURSE Table

16 Figure 6.5 Defining the CODE Field

17 Figure 6.6 Look-up Values

18 Table 6.7

19 Figure 6.7 Access View

20 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.

21 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.

22 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

23 Figure 6.8 Enterprise Data Model

24 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

25 Figure 6.11 Entity-relationship Diagram

26 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.

27 Figure 6.13 Class Diagram

28 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

29 Figure 6.15 Combined Data Entry Form

30 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.

31 Figure 6.16 Report of Departments

32 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.

33 Figure 6.20 SQL Code

34 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.

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

36 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.

37 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.