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Preparing to Automate Data Management
Chapter 1 Preparing to Automate Data Management Use the quote as a jumping off point for discussion, if desired.
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Chapter Introduction Discovery phase includes:
Gathering all existing data Researching missing and incomplete data Talking with users about data output needs Subsequent steps in process include: Putting data into groups called tables Identifying unique values for each record in those tables Designing database to produce desired output Succeeding in Business with Microsoft Access 2010
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Database Design Process: The Discovery Phase
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Level 1 Objectives: Examining Existing and Missing Sources of Data
Discover and evaluate sources of existing data Research sources of missing data Assign data to tables and use field types and sizes to define data Succeeding in Business with Microsoft Access 2010
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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 Succeeding in Business with Microsoft Access 2010
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Discovering and Evaluating Sources of Existing Data (cont’d)
Data duplication Undesirable Additional space required in database to store extra records Leads to inconsistent and inaccurate data Data redundancy Same data repeated for different records Succeeding in Business with Microsoft Access 2010
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Researching Sources of Missing Data
Part of discovery phase Must ask right questions of right people to get right answers Succeeding in Business with Microsoft Access 2010
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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 Succeeding in Business with Microsoft Access 2010
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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 Succeeding in Business with Microsoft Access 2010
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Evaluating Field Values and Assigning Appropriate Data Types
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 Succeeding in Business with Microsoft Access 2010
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Common Data Types and Their Descriptions
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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 Displays only 65,000 characters Succeeding in Business with Microsoft Access 2010
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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 Succeeding in Business with Microsoft Access 2010
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The Currency Data Type Includes two decimal places and displays values with dollar sign Use for monetary values Succeeding in Business with Microsoft Access 2010
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The Date/Time Data Type
Display values in format mm/dd/yyyy Can also include time in different formats Used in calculations if necessary Succeeding in Business with Microsoft Access 2010
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The AutoNumber Data Type
Number automatically generated by access Produces unique values for each record Useful to distinguish two records that share identical information Succeeding in Business with Microsoft Access 2010
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The Yes/No Data Type Assigned to fields requiring
True/false On/off Takes up one character of storage space Make data entry easy Check box Succeeding in Business with Microsoft Access 2010
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The OLE Object Data Type
Used to identify files created in another program Then linked or embedded in database Abbreviation for object linking and embedding Succeeding in Business with Microsoft Access 2010
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The Hyperlink Data Type
Assigned to fields that contain hyperlinks to Web pages addresses Files that open in Web browser client Another application Succeeding in Business with Microsoft Access 2010
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The Attachment Data Type
Lets you store one or more files for each record in the database Pictures Documents Charts Spreadsheets Succeeding in Business with Microsoft Access 2010
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The Calculated Type New for Access 2010
Uses data from fields in the same table to perform calculations When selected, opens Expression Builder so you can create the calculation or expression Succeeding in Business with Microsoft Access 2010
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The Lookup 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 Succeeding in Business with Microsoft Access 2010
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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 Succeeding in Business with Microsoft Access 2010
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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 Succeeding in Business with Microsoft Access 2010
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Assigning the Correct Field Size for Number Fields
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Dividing the Existing and Missing Data into 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 Succeeding in Business with Microsoft Access 2010
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Database Design Process: Planning the Tables
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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 Succeeding in Business with Microsoft Access 2010
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Leszynski/Reddick Naming Conventions for Database Objects
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Level 1 Summary Discovery phase Identify existing and missing data
Determine tables Determine data types Follow naming conventions Succeeding in Business with Microsoft Access 2010
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Level 2 Objectives: Understanding and Creating Table Relationships
Understand relational database objects and concepts Create table relationships Understand referential integrity Succeeding in Business with Microsoft Access 2010
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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 Succeeding in Business with Microsoft Access 2010
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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 Most of the time, three other main database objects used to display data Succeeding in Business with Microsoft Access 2010
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Queries Query Query results
Question asked about data stored in database Query results Look similar to table Fields displayed in columns Records displayed in rows Succeeding in Business with Microsoft Access 2010
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Queries (continued) Select query Action query Crosstab query
Most commonly used query Data selected from table on which query based Action query Performs action on table Select specific records in table and update them Crosstab query Performs calculations on values in field and displays results in datasheet Succeeding in Business with Microsoft Access 2010
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Forms Used to view, add, delete, and update records in database
Based on table or query Interface more attractive than table datasheet Customize form’s appearance with instructions and command buttons Switchboard or Navigation form Form displayed when database opened Provides controlled method for users to open objects in database Succeeding in Business with Microsoft Access 2010
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Form Based on a Table Succeeding in Business with Microsoft Access 2010
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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 Succeeding in Business with Microsoft Access 2010
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Accounts Receivable Report
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Other Database Objects
Macro Set of instructions Automate certain database tasks Usually automates simple tasks Module Contains instructions to automate database task Written in Visual Basic for Applications (VBA) Performs more sophisticated actions than macro Succeeding in Business with Microsoft Access 2010
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Understanding Relational Database Concepts
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 Succeeding in Business with Microsoft Access 2010
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Creating Table Relationships
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 Succeeding in Business with Microsoft Access 2010
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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 Succeeding in Business with Microsoft Access 2010
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One-to-Many Relationship Between Customers and Prescriptions
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One-to-One Relationships
Abbreviated as 1:1 Exists when each record in one table matches exactly one record in related table Succeeding in Business with Microsoft Access 2010
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One-to-One Relationship Between Physical and Billing Addresses
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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 Succeeding in Business with Microsoft Access 2010
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Many-to-Many Relationship Between Employees and Classes
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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 Succeeding in Business with Microsoft Access 2010
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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 Succeeding in Business with Microsoft Access 2010
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Referential Integrity Errors
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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 Succeeding in Business with Microsoft Access 2010
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Level 2 Summary Main database objects: Relationship types: Table Query
Form Report Relationship types: One-to-many One-to-one Many-to-many Succeeding in Business with Microsoft Access 2010
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Learn the techniques for normalizing data
Level 3 Objectives: Identifying and Eliminating Database Anomalies by Normalizing Data Learn the techniques for normalizing data Evaluate fields that are used as keys Test the database design Succeeding in Business with Microsoft Access 2010
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Normalizing the Tables in the Database
Normalization Design process Goals: Reduces space required to store data by eliminating duplicate data in database Reduces inconsistent data in database by storing data only once Reduces chance of deletion update and insertion anomalies Succeeding in Business with Microsoft Access 2010
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Normalizing the Tables in the Database (continued)
Deletion anomaly User deletes data from database Unintentionally deletes only occurrence of data in database Update anomaly Due to redundant data in database User fails to update some records or updates records erroneously Insertion anomaly User cannot add data to database unless preceded by entry of other data Succeeding in Business with Microsoft Access 2010
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Normalizing the Tables in the Database (continued)
Functional dependency Column in table considered functionally dependent on another column If each value in second column associated with exactly one value in first column Partial dependency Field dependent on only part of primary key Composite primary key Primary key uses two or more fields to create unique records in table Succeeding in Business with Microsoft Access 2010
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Normalizing the Tables in the Database (continued)
Determinant Field or collection of fields whose value determines value in another field Inverse of dependency Natural key Primary key that details obvious and innate trait of record Artificial key Field whose sole purpose is to create primary key Usually visible to users Succeeding in Business with Microsoft Access 2010
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Normalizing the Tables in the Database (continued)
Surrogate key Computer-generated primary key Usually invisible to users Succeeding in Business with Microsoft Access 2010
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First Normal Form Repeating group First normal form
Field contains more than one value First normal form 1NF Does not contain any repeating groups Succeeding in Business with Microsoft Access 2010
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Succeeding in Business with Microsoft Access 2010
Padding up the missing columns won’t remediate redundancy. Succeeding in Business with Microsoft Access 2010
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The solution is to split the “wide” table into two.
Remember to remain the link Succeeding in Business with Microsoft Access 2010
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Second Normal Form 2NF Table must be in 1NF
Must not contain any partial dependencies on composite primary key Tables in 1NF and contain primary key with only one field Automatically in 2NF Succeeding in Business with Microsoft Access 2010
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Still has redundancy Depend on only part of PK Composite PK
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Third Normal Form 3NF Only determinants must be candidate keys
Field or collection of fields that could function as primary key but was not chosen to do so Transitive dependency Occurs between two nonkey fields both dependent on third field Tables in 3NF should not have transitive dependencies Succeeding in Business with Microsoft Access 2010
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Level 3 Summary Normal forms First (1NF) Second (2NF) Third (3NF)
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Chapter Summary Discovery: Table relationships
Identify existing and missing data Organize data into tables Determine data types for each field Table relationships Established through common fields Types 1:M 1:1 M:N Succeeding in Business with Microsoft Access 2010
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Chapter Summary (continued)
Normalization Reduces duplication and inconsistency Forms: 1NF 2NF 3NF Succeeding in Business with Microsoft Access 2010
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