Accounting Information Systems - Relational Databases

8/3/2019 Accounting Information Systems - Relational Databases

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Chapter 4

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1. Explain the difference between database and file-based legacy systems.

2. Describe what a relational database is and how it

organizes data.3. Explain the difference between logical and physical

views of a database.4. Create a set of well-structured tables to properly store

data in a relational database.

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Ashton Fleming, the accountant for S&S,

believes that the best way to provide Susan

Gonzalez and Scott Parry with easy access tothe information they need to run their

business is to build S&Ss new AIS as adatabase system.

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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?

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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 adatabase.

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Data a collection of facts made up of text, numbersand dates:

Murray 35000 7/18/86

Information - the meaning given to data in the way it isinterpreted:

Mr. Murrayis a sales person whose annualsalaryis$35,000 andwhose hire date isJuly 18, 1986.

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Data Information Knowledge Action

Is to transformIs to transform

Data driven decision makingData driven decision making

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What is a file?

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A structured collection of related data

An filing cabinet, an address book, atelephone directory, a timetable, etc.

Google and your email is a database

School Student Information System


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Records

Fields

Name GatorLink Phone College

Graff rgraff 392-3900 Pharmacy

Harris bharris 392-5555 Medicine

Ipswich zipswich 846-5656 PHHP

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Name User Phone College

Graff rgraff 392-3900 Pharmacy

Harris bharris 392-5555 Medicine

Ipswich zipswich 846-5656 PHHP

To ensure that each record is unique in each table, we

can set one field to be aPrimary Key field.

A Primary Key is a field that that will contain no

duplicates and no blank values.

Foreign Keys link to data in other tables

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A set of all related records forms afile (e.g., thestudent file).

I

f this university only had three students and fivefields for each student, then the entire file would bedepicted below.

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A set of interrelated, centrally coordinated filesforms a database.

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Two basic types of files are used to store

data.

1 The masterfile, which is similar to a ledger in

a manual system.

2 The transactionfile, which is similar to a

journal in a manual system.

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For many years, companies created new files

and programs each time an information need

arose.

This increase of master files created

problems:1 Often the same data was stored in two or more separate files.

2 The specific data values stored in the different files were not

always consistent.

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Shipping

Program

Sales

Program

File 1

Fact A

Fact B

Fact C

File 2

Fact B

Fact D

Fact E

Billing

Program

File 3

Fact A

Fact G

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The database approach views data as anorganizational resource that should be used by, andmanaged 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 filesinto larger pools of data that can be accessed bymany application programs.

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Database managementsystem (DBMS) is theprogram that manages and controls access to

the database.

Database system is the combination of thedatabase, theDBMS, and the application

program that uses the database.

Database administrator(DBA) is the personresponsible for the database.

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BillingProgram

Shipping

Program

Databasemanagement

system

Sales Program

Fact A

Fact B

Fact C

Fact D

Fact E

Database

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As accountants, you are likely to audit or workfor companies that use database technology tostore, process, and report accountingtransactions.

Many accountants work directly with databases andwill enter, process, and query databases.

Some will develop and evaluate internal controlsnecessary to ensure database integrity.

Others will be involved in the design andmanagement of databases.

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Describe what a relational

database is and how itorganizes data.

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Adata modelis an abstract representation of

the contents of a database.

The relationaldata modelrepresents

everything in the database as being stored inthe form of tables.

Technically, these tables are called relations.

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Each row in a relation, called a tuple, contains

data about a specific occurrence of the type

of entity represented by that table.

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A relational database is a collection of tables fromwhich data can be accessed in many different wayswithout having to reorganize the database tables.

DONTDUPLICATEDATA

That is, once relationships are created, tables can talk

to each other. We can link (relate) the tables to find: Which schools are in a system?

Which students are in which class?

Which classes are filling up?


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Relationships

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Explain the difference between logical and

physical views of a database.

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A major advantage of database systems over

file-oriented systems is that the database

systems separate the logical and physicalview of data.

What is the logical view?

It is how the user or programmer conceptuallyorganizes and understands the data.

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What is the physical view?

It refers to how and where the data are physically

arranged and stored on disk, tape, CD-ROM, orother media.

TheDBMS controls the database so that

users can access, query, or update it without

reference to how or where the data arephysically stored.

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Program-data independence is the

separation of the logical andphysical views of data.

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A schema describes the logical structure of a

database.

There are three levels of schemas:1 Conceptual-level schema

2 External-level schema

3 Internal-level schema

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The conceptual-level schema is an organization-wide view of the entire database.

The external-level schema consists of a set ofindividual user views of portions of the database,also referred to as a subschema.

The internal-level schema provides a low-levelview of the database.

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The data dictionarycontains information

about the structure of the database.

For each data element stored in thedatabase, such as the customer number,

there is a corresponding record in the datadictionary describing it.

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The data dictionary is often one of the firstapplications of a newly implementeddatabase 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

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What are some outputs of the datadictionary? reports useful to programmers, database

designers, and users of the informationsystem

What are some sample reports? lists of programs in which a data item is

used

lists of all synonyms for the dataelements in a particular file

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EveryDBMS must provide a means ofperforming the three basic functions:1 Creating the database

2 Changing the database3 Querying the database

The sets of commands used toperform these functions are referred

to as the data definition, datamanipulation, and data querylanguages.

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The data definition language (DDL) is usedto... build the data dictionary.

initialize or create the database.

describe the logical views for each individual useror programmer.

specify any limitations or constraints on securityimposed on database record or fields.

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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

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The data query language (DQL) is used to

interrogate the database.

TheDQL retrieves, sorts, orders, andpresents subsets of the database in response

to user queries.

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Create a set of well-structured tables to

properly store data in a relational database.

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1. Each column in a row must be single valued.2. Primary keys cannot be null.3. Foreign keys, if not null, must have values that

correspond to the value of a primary key in an otherrelation.

4. All non-key attributes in a table should describe acharacteristic about the object identified by the

primary key.

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UpdateAnomaly: When changes (updates)to data values are not correctly recorded.

Instead of having to update once, each recordin the single table has to be updatedindividually in order to avoid inconsistencies inthe database.

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InsertAnomaly:There is no way to store

information about one entity in the database

without it being associated with anotherentity

In the text, we would not be able to storeinformation on new customers without their

being associated with transactions first!

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DeleteAnomaly:Unintended results arisingfrom deleting a row of data pertaining to oneentity 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 databasetable, we would lose information on the customerassociated with that inventory item as well.

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Normalization

Starts with the assumption that all data is initially stored ina large non-normalized table.

This table is then decomposed using a set of normalizationrules to create a set of tables in the ThirdNormal Form.

SemanticDataModeling

The database designer uses his/her knowledge about thebusiness structure to create a set of relational tables.

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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 thataccounting information is used in decision

making.

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Accounting Information Systems - Relational Databases