1. Accounting Information Systems 9th Edition
Marshall B. Romney
Paul John Steinbart
©2003 Prentice Hall Business Publishing,
Accounting Information Systems, 9/e, Romney/Steinbart

2. Relational Databases Chapter 4
©2003 Prentice Hall Business Publishing,
Accounting Information Systems, 9/e, Romney/Steinbart

3. Learning Objectives
Explain the difference between database and file-based legacy systems.
Describe what a relational database is and how it organizes data.
Explain the difference between logical and physical views of a database.
Create a set of well-structured tables to properly store data in a relational database.
©2003 Prentice Hall Business Publishing,
Accounting Information Systems, 9/e, Romney/Steinbart

4. Introduction
Ashton Fleming, the accountant for S&S, believes that the best way to provide Susan Gonzalez and Scott Parry with easy access to the information they need to run their business is to build S&S’s new AIS as a database system.
©2003 Prentice Hall Business Publishing,
Accounting Information Systems, 9/e, Romney/Steinbart

5. Introduction
Ashton decides to prepare a brief report for them addressing the following questions:
What is a database system?
What is a relational database system?
How do you design a relational database?
©2003 Prentice Hall Business Publishing,
Accounting Information Systems, 9/e, Romney/Steinbart

6. Introduction
This chapter explains what a database is and how it differs from a file-oriented system.
It also describes the structure of a relational database system.
The chapter concludes by discussing the basic steps involved in designing a database.
©2003 Prentice Hall Business Publishing,
Accounting Information Systems, 9/e, Romney/Steinbart

7. Learning Objective 1
Explain the difference between database and file-based legacy systems.
©2003 Prentice Hall Business Publishing,
Accounting Information Systems, 9/e, Romney/Steinbart

8. Types of Files Two basic types of files are used to store data.
The master file, which is conceptually similar to a ledger in a manual system.
The transaction file, which is conceptually similar to a journal in a manual system.
©2003 Prentice Hall Business Publishing,
Accounting Information Systems, 9/e, Romney/Steinbart

9. File Approach
For many years, companies created new files and programs each time an information need arose.
This proliferation of master files created problems:
Often the same data was stored in two or more separate files.
The specific data values stored in the different files were not always consistent.
©2003 Prentice Hall Business Publishing,
Accounting Information Systems, 9/e, Romney/Steinbart

10. File-Oriented Approach
Shipping
Program
Sales
File 1
Fact A Fact B Fact C
File 2
Fact B Fact D Fact E
Billing
File 3
Fact A Fact G Fact E
©2003 Prentice Hall Business Publishing,
Accounting Information Systems, 9/e, Romney/Steinbart

11. Databases
The database approach views data as an organizational resource that should be used by, and managed for, the entire organization, not just the originating department or function.
Its focus is data integration and data sharing.
Integration is achieved by combining master files into larger pools of data that can be accessed by many application programs.
©2003 Prentice Hall Business Publishing,
Accounting Information Systems, 9/e, Romney/Steinbart

12. Databases
Database management system (DBMS) is the program that manages and controls access to the database.
Database system is the combination of the database, the DBMS, and the application program that uses the database.
Database administrator (DBA) is the person responsible for the database.
©2003 Prentice Hall Business Publishing,
Accounting Information Systems, 9/e, Romney/Steinbart

13. Database Approach Sales Program Database Fact A Fact B Database Fact C
Fact D
Fact E
Database
management
system
Shipping
Program
Billing
Program
©2003 Prentice Hall Business Publishing,
Accounting Information Systems, 9/e, Romney/Steinbart

14. Describe what a relational database is and how it organizes data.
Learning Objective 2
Describe what a relational database is and how it organizes data.
©2003 Prentice Hall Business Publishing,
Accounting Information Systems, 9/e, Romney/Steinbart

15. Relational Databases
A data model is an abstract representation of the contents of a database.
The relational data model represents everything in the database as being stored in the form of tables.
Technically, these tables are called relations.
©2003 Prentice Hall Business Publishing,
Accounting Information Systems, 9/e, Romney/Steinbart

16. Relational Databases
Each row in a relation, called a tuple, contains data about a specific occurrence of the type of entity represented by that table.
©2003 Prentice Hall Business Publishing,
Accounting Information Systems, 9/e, Romney/Steinbart

17. Learning Objective 3
Explain the difference between logical and physical views of a database.
©2003 Prentice Hall Business Publishing,
Accounting Information Systems, 9/e, Romney/Steinbart

18. Logical and Physical Views of Data
A major advantage of database systems over file-oriented systems is that the database systems separate the logical and physical view of data.
What is the logical view?
It is how the user or programmer conceptually organizes and understands the data.
©2003 Prentice Hall Business Publishing,
Accounting Information Systems, 9/e, Romney/Steinbart

19. Logical and Physical Views of Data
What is the physical view?
It refers to how and where the data are physically arranged and stored on disk, tape, CD-ROM, or other media.
The DBMS controls the database so that users can access, query, or update it without reference to how or where the data are physically stored.
©2003 Prentice Hall Business Publishing,
Accounting Information Systems, 9/e, Romney/Steinbart

20. Logical and Physical Views of Data
Logical View User A
Logical View User B
Past Due Accounts
Name Balance Days
Jackson
Houston
October Sales by Region
Database
DBMS
Operating
system
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Accounting Information Systems, 9/e, Romney/Steinbart

21. Logical and Physical Views of Data
Program-data independence is the separation of the logical and physical views of data.
©2003 Prentice Hall Business Publishing,
Accounting Information Systems, 9/e, Romney/Steinbart

22. Schemas A schema describes the logical structure of a database.
There are three levels of schemas:
Conceptual-level schema
External-level schema
Internal-level schema
©2003 Prentice Hall Business Publishing,
Accounting Information Systems, 9/e, Romney/Steinbart

23. Schemas
The conceptual-level schema is an organization-wide view of the entire database.
The external-level schema consists of a set of individual user views of portions of the database, also referred to as a subschema.
The internal-level schema provides a low-level view of the database.
©2003 Prentice Hall Business Publishing,
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24. Mapping external level views to conceptual level schema
Schemas
Subschema A
Subschema B
Subschema C
Jackson
Houston r r
xxxxxxx
Mapping external level views to conceptual level schema
Inventory
Sales
Customer
Cash receipt
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25. Schemas Inventory Sales Customer Cash receipt
Mapping conceptual level facts to internal level descriptions
Inventory Record Item number – integer (5), non-null, index = itemx Description – character (15)
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Accounting Information Systems, 9/e, Romney/Steinbart

26. The Data Dictionary
The data dictionary contains information about the structure of the database.
For each data element stored in the database, such as the customer number, there is a corresponding record in the data dictionary describing it.
©2003 Prentice Hall Business Publishing,
Accounting Information Systems, 9/e, Romney/Steinbart

27. The Data Dictionary
The data dictionary is often one of the first applications of a newly implemented database system.
What are some inputs to the data dictionary?
records of any new or deleted data elements
changes in names, descriptions, or uses of existing data elements
©2003 Prentice Hall Business Publishing,
Accounting Information Systems, 9/e, Romney/Steinbart

28. The Data Dictionary What are some outputs of the data dictionary?
reports useful to programmers, database designers, and users of the information system
What are some sample reports?
lists of programs in which a data item is used
lists of all synonyms for the data elements in a particular file
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29. DBMS Languages
Every DBMS must provide a means of performing the three basic functions:
Creating the database
Changing the database
Querying the database
The sets of commands used to perform these functions are referred to as the data definition, data manipulation, and data query languages.
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Accounting Information Systems, 9/e, Romney/Steinbart

30. DDL Language The data definition language (DDL) is used to...
build the data dictionary.
initialize or create the database.
describe the logical views for each individual user or programmer.
specify any limitations or constraints on security imposed on database record or fields.
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31. DML Language
The data manipulation language (DML) is used for data maintenance.
What does it include?
updating portions of the database
inserting portions of the database
deleting portions of the database
©2003 Prentice Hall Business Publishing,
Accounting Information Systems, 9/e, Romney/Steinbart

32. DQL Language
The data query language (DQL) is used to interrogate the database.
The DQL retrieves, sorts, orders, and presents subsets of the database in response to user queries.
©2003 Prentice Hall Business Publishing,
Accounting Information Systems, 9/e, Romney/Steinbart

33. Learning Objective 4
Create a set of well-structured tables to properly store data in a relational database.
©2003 Prentice Hall Business Publishing,
Accounting Information Systems, 9/e, Romney/Steinbart

34. Basic Requirements of the Relational Data Model
Each column in a row must be single valued.
Primary keys cannot be null.
Foreign keys, if not null, must have values that correspond to the value of a primary key in an other relation.
All non-key attributes in a table should describe a characteristic about the object identified by the primary key.
©2003 Prentice Hall Business Publishing,
Accounting Information Systems, 9/e, Romney/Steinbart

35. Anomalies That May Occur in Non-Normalized Relational Tables
Update Anomaly: When changes (updates) to data values are not correctly recorded.
Instead of having to update once, each record in the single table has to be updated individually in order to avoid inconsistencies in the database.
©2003 Prentice Hall Business Publishing,
Accounting Information Systems, 9/e, Romney/Steinbart

36. Anomalies That May Occur in Non-Normalized Relational Tables
Insert Anomaly: There is no way to store information about one entity in the database without it being associated with another entity
In the text, we would not be able to store information on new customers without their being associated with transactions first!
©2003 Prentice Hall Business Publishing,
Accounting Information Systems, 9/e, Romney/Steinbart

37. Anomalies That May Occur in Non-Normalized Relational Tables
Delete Anomaly: Unintended results arising from deleting a row of data pertaining to one entity and resulting in the deletion of data regarding another entity as well.
In the text, if a particular Inventory item were discontinued and hence removed from the database table, we would lose information on the customer associated with that inventory item as well.
©2003 Prentice Hall Business Publishing,
Accounting Information Systems, 9/e, Romney/Steinbart

38. Approaches to Database Design
Normalization
Starts with the assumption that all data is initially stored in a large non-normalized table.
This table is then decomposed using a set of normalization rules to create a set of tables in the Third Normal Form.
Semantic Data Modeling
The database designer uses his/her knowledge about the business structure to create a set of relational tables.
©2003 Prentice Hall Business Publishing,
Accounting Information Systems, 9/e, Romney/Steinbart

39. Database Systems and the Future of Accounting
Database systems have the potential to significantly alter the nature of external reporting.
Perhaps the most significant effect of database systems will be in the way that accounting information is used in decision making.
©2003 Prentice Hall Business Publishing,
Accounting Information Systems, 9/e, Romney/Steinbart

40. End of Chapter 4 ©2003 Prentice Hall Business Publishing,
Accounting Information Systems, 9/e, Romney/Steinbart