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CSE 2337Introduction to

Data Management

Access Book – Ch 1

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DB Design Process: Discovery Phase

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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 • Microsoft Access• MySQL

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One Goal

Reduce Data Duplication and Redundancy.

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Considering Different Types of Data

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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– Stores maximum of 65,535 characters

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The Number Data Type

• Stores both positive and negative numbers

• Contains up to 15 digits• Use for values used in calculations

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AutoNumber

• 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

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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

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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

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Assigning the Correct Field Size for Number Fields

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Naming Conventions

• Database tables must – Have unique names– Follow established naming conventions

• General rules for naming objects– Object names cannot exceed 64 characters– Object names cannot include period,

exclamation point, accent grave, or brackets– Object names should not include spaces– Most developers capitalize first letter of each

word when table name includes two words

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Leszynski/Reddick Naming Conventions

I don’t particularly care!!!

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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

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Tables

• Data in relational database stored in one or more tables

• View data in table – Open it and scroll through records

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Queries

• Query – Question asked about data stored in

database

• Query results– Look similar to table– Fields displayed in columns – Records displayed in rows

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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

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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

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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 relationship

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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

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One – to - one

• Abbreviated as 1:1• Exists when each record in one table

matches exactly one record in related table

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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

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Integrity

• 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

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Integrity Errors