Lecture Accounting information systems: Chapter 4 - Richardson, Chang, Smith

Chapter 4 - Relational databases and enterprise systems. In this chapter students will be able to: Describe the advantages of relational databases, explain basic relational database principles, describe how to query using Structured Query Language (SQL), understand the purpose and basic framework for an enterprise system, assess how cloud computing facilitates enterprise systems.

Chapter 4

Relational Databases and

Enterprise Systems

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• LO#1 Describe the advantages of relational databases.

• LO#2 Explain basic relational database principles.

• LO#3 Describe how to query using Structured Query

Introduction of Database

for various uses

Three types of data models:

• A Hierarchical data model organizes data

into a tree-like structure that allows

repeating information using defined

parent/child relationships

• A Network data model is a flexible model

representing objects and their relationships

• A Relational data model is a data model

that stores information in the form of related

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Introduction of Database

• Relational data models are the dominant data model

form in use today likely because they offer many

advantages over other data models, including:

§ Flexibility and Scalability

§ Simplicity

§ Reduced Information Redundancy

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Definitions for Databases

• Database Management System (DBMS) – The DBMS

is defined as a computer program that creates, modifies and queries the database Specifically, the DBMS is

designed to manage a database’s storage and retrieval

of information

• Data Dictionary – The data dictionary describes the

data fields in each database record such as field

description, field length, field type (e.g., alphanumeric,

numeric), etc

• Database Administrator – The person responsible for

the design, implementation, repair and security of a

firm’s database

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Fundamentals of Relational Databases

• A class in the relational database model could be a

person, place, thing, transaction, or event about which

information is stored Classes could be grouped into

resources (R), events (E), and agents (A) in data

modeling

• Attributes are characteristics, properties, or adjectives

that describe each class

• A primary key is an attribute or combination of attributes that uniquely identify a specific row in a table

• A foreign key in the relational database model serves as

an attribute in one table that is a primary key in another

table A foreign key acts to provide a logical relationship,

or a link, between two tables

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Fundamentals of Relational Databases

• Table/Relation: The primary construct, used for data

storage with rows and columns much like a spreadsheet Each table in a database represents either a class or a

relationship between classes Tables need to be

properly linked to make a relational database

• Column: The columns in a table are called fields that

represent the attributes or characteristics of the class or

relationship

• Rows: The rows in a table are called records or tuples

The records represent all the specific data values that

are associated with one instance 4-7

Fundamentals of Relational Databases

• Basic Requirements of Tables

• The Entity Integrity Rule: the primary key of a table

must have data values (cannot be null)

• The Referential Integrity Rule: the data value for a

foreign key must either be null or match one of the data

values that already exist in the corresponding table

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Fundamentals of Relational Databases

• Basic Requirements of Tables

name.

same type

be single-valued This requirement forces us to create a relationship table for each many-to-

many relationship

describe a characteristic of the class (table)

identified by the primary key

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Microsoft Access to Implement a

Relational Database

• Introduction to Microsoft Access

Access is a simple database management system that

can be used to run databases for individuals and small

firms

The Access system is composed of seven objects that

are used to implement relational databases

Tables are used to store data which consists of a series

of rows (records) and columns (attributes) connected by

relationships (links between tables)

Queries are a tool used to retrieve and display data

derived from records stored within the database

Forms are utilized by users to enter data into tables and

view existing records

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Microsoft Access to Implement a

Relational Database

• Reports are used to integrate data from one or more

queries and tables to provide useful information to

decision makers

• Pages, Web-based forms, allow data to be entered into

the database in real time from outside of the database

system

• Macros are defined by users to automate processes like

opening a specific form

• Access’s code can be altered by the use of modules

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Structured Query Language (SQL)

Structured Query Language and is a computer

language designed to query data in a relational

database

• SQL is based on relational algebra and allows a user to

query and update the database

• In a database, while queries allow the user to access,

read and report on desired data, the responsibility of

actually making physical changes to the relational

database belongs to the Database Management

System (DBMS).

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Structured Query Language (SQL)

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a query

which columns (or attributes) of a table

should be included in the query

statement indicates the name of table(s)

from which to retrieve data

Structured Query Language (SQL)

must be met to be shown in the query

result

aggregate functions on the query results

based on one or more columns

columns are used to sort the resulting data

If there is no ORDER BY clause, the order

of rows returned by an SQL query will not

Structured Query Language (SQL)

• SELECT DISTINCT clause selects a column

without showing repetitive values

• The BETWEEN operator can be used to specify

the end points of a range

• Membership Operator (IN) allows you to test

whether a data value matches the specified

target values

Structured Query Language (SQL

Six relational operators in SQL

Relational Operators Meaning

Structured Query Language (SQL

SQL language provides several convenient

aggregate functions to be used in SQL commands These aggregate functions include AVG, SUM,

MAX, MIN, and COUNT Their definitions are as

follows:

satisfy the selection criteria for column X.

satisfy the given condition.

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Enterprise Systems

Enterprise systems (ES), also known as Enterprise

Resource Planning (ERP) systems, are commercialized

information systems that integrate and automate business

processes across a firm’s value chain located within and

across organizations Typically, an enterprise system uses

relational data model as a basis for the information

system The use of primary and foreign keys links the

hundreds of tables that form the basis for the enterprise

system

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In fact, for a popular ERP product (SAP/ERP) installation, there are

10,000 tables that are all linked to each other!

Enterprise Systems

• ES accommodates the integration and support of the

various business processes and information needs of a

company

• ES has a higher level of internal transparency compared

to the typically isolated legacy systems

• The purported informational benefits of an enterprise

system include enhanced completeness, transparency,

and timeliness of information needed to manage

effectively an organization’s business activities

• The enterprise system serves as the backbone of the

company’s internal business processes and serves as a connection with the external business processes for

supply chain and customer relationship management

systems

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Enterprise Systems

Challenges of Enterprise System Implementation

• integrating various modules within the enterprise system,

• integrating with external systems such as the information system of a supplier and/or customer,

• integrating with the firm’s own existing legacy systems,

• converting data from existing legacy systems to the

enterprise system, and

• getting any big project implemented at a firm

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Enterprise Systems

Enterprise Systems Computing in a Cloud

• In recent years, cloud computing has emerged as a

potential alternative to host enterprise systems and other firm computing needs

• Cloud computing is Internet-based computing where

shared resources, software, and information are

provided to firms on demand

• Cloud Computing can easily host enterprise system

applications

• Cloud computing, of course, has disadvantages as

well Ensuring that any sensitive data is secure and

backed up frequently by the host is often a concern of

cloud computing clients

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