information systems

INFORMATION SYSTEM

Lecture # 12

CHAPTER 5 (CONTINUED)ORGANIZING DATA AND

INFORMATION

Principles of Information

Systems(Eighth Edition)

DATA MODELING AND THE RELATIONAL DATABASE MODEL

When building a database, an organization must consider: Content: What data should be collected and at

what cost? Access: What data should be provided to which

users and when? Logical structure: How should data be arranged

so that it makes sense to a given user? Physical organization: Where should data be

physically located?

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DATA MODELING

Building a database requires two types of designs Logical design: abstract model of how the data

should be structured and arranged to meet an organization’s information needs

Physical design: starts from the logical database design and fine-tunes it for performance and cost considerations

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DATA MODELING (CONTINUED)

Data model: 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

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DATA MODELING (CONTINUED)

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Figure 5.4: An Entity-Relationship (ER) Diagram for a Customer Order Database

THE RELATIONAL DATABASE MODEL

Relational model: describes data in which all data elements are placed in two-dimensional tables, called relations, that are the logical equivalent of files Each row of a table represents a data entity Columns of the table represent attributes Domain: allowable values for data attributes

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THE RELATIONAL DATABASE MODEL (CONTINUED)


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8Figure 5.5: A Relational Database Model


Selecting: eliminates rows according to certain criteria

Projecting: eliminates columns in a table Joining: combines two or more tables Linking: manipulating two or more tables

that share at least one common data attribute to provide useful information and reports

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Figure 5.6: A Simplified ER Diagram Showing the Relationship Between the Manager, Department, and Project Tables


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Figure 5.7: Linking Data Tables to Answer an Inquiry


Data cleanup: process of looking for and fixing inconsistencies to ensure that data is accurate and complete Eliminate redundancies and anomalies



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Table 5.3: Fitness Center Dues



Table 5.5: Dues Paid

Table 5.4: Fitness Center Members

DATABASE MANAGEMENT SYSTEMS (DBMSS)

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Creating and implementing the right database system ensures that the database will support both business activities and goals

DBMS: a group of programs used as an interface between a database and application programs or a database and the user

OVERVIEW OF DATABASE TYPES

Flat file Simple database program whose records have no

relationship to one another Single user

Only one person can use the database at a time Examples: Access, FileMaker, and InfoPath

Multiple user Allows dozens or hundreds of people to access

the same database system at the same time Examples: Oracle, Sybase, and IBM

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PROVIDING A USER VIEW

Schema: description of the entire database Typically used by large database systems to

define tables and other database features associated with a person or user

A DBMS can reference a schema to find where to access the requested data in relation to another piece of data

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CREATING AND MODIFYING THE DATABASE

Data definition language (DDL): collection of instructions and commands used to define and describe data and relationships in a specific database Allows the database’s creator to describe the

data and relationships that are to be contained in the schema

Data dictionary: detailed description of all the data used in the database

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CREATING AND MODIFYING THE DATABASE (CONTINUED)


Figure 5.10: Using a Data Definition Language to Define a Schema

CREATING AND MODIFYING THE DATABASE (CONTINUED)


Figure 5.11: A Typical Data Dictionary Entry

STORING AND RETRIEVING DATA

When an application program requests data from the DBMS, the application program follows a logical access path

When the DBMS goes to a storage device to retrieve the requested data, it follows a path to the physical location (physical access path) where the data is stored

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STORING AND RETRIEVING DATA (CONTINUED)


Figure 5.12: Logical and Physical Access Paths

MANIPULATING DATA AND GENERATING REPORTS

Data manipulation language (DML): commands that manipulate the data in a database

Structured Query Language (SQL) Adopted by the American National Standards

Institute (ANSI) as the standard query language for relational databases

Once a database has been set up and loaded with data, it can produce reports, documents, and other outputs

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MANIPULATING DATA AND GENERATING REPORTS (CONTINUED)


Table 5.6: Examples of SQL Commands

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