Preparing to Automate Data Management

Preparing to Automate Data Management

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Chapter 1

“You can use all the quantitative data you can get, but you stillhave to distrust it and use your own intelligence and judgment.” — Alvin Toffler

Discovering and Evaluating Sources of Existing Data• Identify information that organization needs to

manage and organize• Might begin to see patterns that indicate how to

organize data• Database management system (DBMS)

– Includes:• Oracle • ColdFusion• Microsoft Access• MySQL

Succeeding in Business with Microsoft Office Access 2007: A Problem-Solving Approach 5

Assimilating the Available Information and Planning the Database• First step in database design

– Determine best way to organize data into logical groups of fields

• Field – Single characteristic of entity– Also called column

• Record– Values in each field in table– Also called row


Assimilating the Available Information and Planning the Database (continued)• Table

– Collection of fields that describe one entity– Also called entity or relation

• Database– Collection of one or more tables

• Relational database– Contains related tables through fields that contain

identical data


Evaluating Field Values and Assigning Appropriate Data Types• Data type

– Determines how to store data in field• DBMSs use different names for some data types• How do you determine which data type to assign

each field? – Depends on what function you want to derive from

data– Each data type has different properties


Common Data Types and Their Descriptions


The Text and Memo Data Types• Text data type

– Letters and numbers– Not used in calculations or formulas– Stores maximum of 255 characters– Default for all fields created in access database

• Memo data type– Store long passages of text– Displays only 64,000 characters


The Number Data Type• Stores both positive and negative numbers • Contains up to 15 digits• Use for values used in calculations


The Currency Data Type• Includes two decimal places and displays values

with dollar sign• Use for monetary values


The Date/Time Data Type• Display values in format mm/dd/yyyy

– Can also include time in different formats• Used in calculations if necessary


The AutoNumber Data Type• Unique to Access• Number automatically generated by access • Produces unique values for each record• Useful to distinguish two records that share

identical information• Produces values of up to nine digits


The Yes/No Data Type• Assigned to fields requiring

– Yes/no– True/false– On/off

• Takes up one character of storage space• Make data entry easy

– Check box


The Lookup Wizard Data Type• Creates fields to look up data in

– Another table– Or list of values created for field

• Makes data entry easy • Ensures that valid data entered into field


Selecting the Correct Data Type• Helps store correct data in correct format while

using least amount of space• Eases data entry and interactivity with data • Choosing certain data types results in user-

friendly interactive features– Drop-down menus – Check boxes– Hyperlinks

• Correctly manipulate data


Assigning the Correct Field Size for Text Fields• Important to consider field size when assigning

data types– Minimize space reserved for each record by assigning

smallest data type that will store data• Be conservative when assigning field sizes

– But not too conservative


Assigning the Correct Field Size for Number Fields


Dividing the Existing and Missing Data into Tables• Tables

– Single most important component of database– Most databases contain

• Multiple tables • Hundreds or even thousands of records

• Primary key – One field that creates unique value in each record – Used to identify each record in table– May be a combination of fields


Leszynski/Reddick Naming Conventions for Database Objects


Understanding Relational Database Objects• Users can view data in tables by:

– Opening table – Creating other objects

• Four main objects in database – Tables– Queries– Forms– Reports


Tables• Data in relational database stored in one or more

tables• View data in table

– Open it and scroll through records• Most of the time, three other main database

objects used to display data normally


Queries• Query

– Question asked about data stored in database• Query results

– Look similar to table– Fields displayed in columns – Records displayed in rows


Forms• Used to view add delete, update and print records in

database• Based on table or query• Interface more attractive than table datasheet• Customize form’s appearance with instructions and

command buttons• Switchboard

– Form displayed when database opened– Provides controlled method for users to open objects in

database


Form Based on a Table


Reports• Formatted presentation of data from table or

query • Created as printout or to be viewed on screen• Data displayed by report usually based on query• Dynamic

– Reflect latest data from object• Cannot be used to modify data


Accounts Receivable Report


Understanding Relational Database Concepts• Flat file database

– Simple database – Contains single table of information

• Relational database– Contains multiple tables to store related information

• Common field – Field that appears in two or more tables and contains

identical data to relate tables– Primary key in first table– Foreign key in second table


Creating Table Relationships• Take advantage of interrelated objects• Goal in good database design

– Create separate tables for each entity– Ensure each table has primary key– Use common field to relate tables

• Relate two (or more) tables– Query them as though they are one big table

• Join – Specifies relationship between tables and properties

of relationshipSucceeding in Business with Microsoft Office Access 2007: A Problem-Solving Approach 41

One-to-Many Relationships• Abbreviated as 1:M• One record in first table matches zero one or

many records in related table• Primary table

– One side• Related table

– Many side


One-to-Many Relationship Between Customers and Prescriptions


One-to-One Relationships• Abbreviated as 1:1• Exists when each record in one table matches

exactly one record in related table


One-to-One Relationship Between Physical and Billing Addresses


Many-to-Many Relationships• Abbreviated as M:N• Each record in first table matches many records

in second table• Each record in second table matches many

records in first table• Junction table


Many-to-Many Relationship Between Employees and Classes


Understanding Referential Integrity• Null value

– Field does not contain any value• Entity integrity

– Guarantee that there are no duplicate records in table– Each record unique– No primary key field contains null values

• Referential integrity – If foreign key in one table matches primary key in second table – Values in foreign key must match values in primary key


Understanding Referential Integrity (continued)• When database does not enforce referential

integrity – Problems occur that lead to inaccurate and

inconsistent data• Orphaned

– No longer match between primary key in primary table and foreign keys in related table


Referential Integrity Errors


Overriding Referential Integrity• Might want to override referential integrity

– Intentionally change primary key – Delete parent record

• Cascade updates– Change primary key value so that DBMS

automatically updates appropriate foreign key values in related table

• Cascade deletes


Preparing to Automate Data Management

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