Adamson & Venerable Chapter 2 &

working out a Homework 5/6 Solution

TransformingRelational Databases into Dimensional

Diagrams

Spring 2012

Dimensional modeling in Sales

• In a DW designed to analyze SALES data, important component of a dimensional model is the Product Dimension.

• Product dimension includes important characteristics used to differentiate the product in the marketplace, called Discriminators.

Key Business Term: Discriminators

• Discriminators: Descriptive characteristics of a product that further describe it and are relevant to purchasing decisions. Tracking discriminators allows the business analyst to monitor performance of various product styles, influencing production and marketing plans.

• Discriminators for a men’s suit: Cloth, color, style/cut, weight, size

• Discriminators for vehicles: Model name, model styling package, line, category, exterior color, model year, interior color

Other Dimensions in Sales

• Time dimension: Time key, month, day, date, year, day of week, quarter.

• Customer_Demographic dimension: This does not require a row for each customer, but groups customers by different combinations of age, gender, income, and geography. The degree of demographic segmentation varies by industry.

• Dealer dimension: Data on dealer performance are needed, to support decisions on which dealers should be eased out of business.

• Method_Of_Payment dimension (lease, financing options, etc.)

Fact Table: Storing derived facts

• A commonly used derived fact should be stored, and not calculated in reports and queries. Cutting such “redundant” key measures from the fact table results in the following:

1. Development of reports gets more complex2. Increased potential for errors in reports3. Increased documentation requirements4. A Hundred dollars’ worth of disk space is

saved (40 MB of space savings for a 10-million row fact table)

Transformation Stages(Key for Homework #5/6)

• De-normalization Process– Start with Normalized Tables– Determine Dimensions and Fact Tables– Delete Relationships

• Rebuild Tables• Rebuild Relationship Diagram as Star

Diagram, a.k.a., Dimension Table• Provides information needed to complete

Homework 6, too!

Premiere Products ERD

Redrawn to form mostlikely Star Diagram

Delete Relationships

Rebuild Tables• Using copied operations database• Be sure all ops. data is saved and backed up …

multiple times.• Data staging & cleansing

– Denormalize extra relationships• Order:OrderLine; • Customer:SalesRep;• Order:OrderLine OrderDetail• Customer:SalesRep OrderDetail

– Transform data for new tables in Access: Make Table– Export data files, if needed, to rebuild elsewhere (Excel)– Additional Transformations as needed in Excel– Create the Time dimension– Re-Import data files to new tables

Order_OrderLine Query

Restructured Data -- Stage 1

Preparing Rep:Customer

Join to Order_OrderLine

OrderDetail Query

Order of Columns Not criticalSort order not critical butGood time to revise

Make-Table OrderDetail Query

OrderDetail TableSet Primary Keys

Data Cleansing

Fix dates

Add Indexes

Build Star Diagram

What’s Missing?

Fact Table

Time DimensionUse SQL to eliminate Redundant dates

Built-in Functions

Built-in Date/Time Functions

Excel Time Table

Create Time table usingExcel Formulas:1. Fill2. Copy/paste3. Compute Quarter4. Conversion Formulas5. Etc.

Import Time Table to Access

Time Table w/Indexes

Premier Products Star Diagram

PP -- Relation List

Fact Table• OrderDetail[OrderNum, PartNum, OrderDate, CustNo,

RepNo, NumOrdered, Price]

Dimension Tables• Customer[CustNum, CustName, Street, City, State, Zip,

Balance, CreditLimit]• Rep[RepNum, LastName, FirstName, Street, City, State,

Zip, Commission, Rate]• Part[PartNum, Desc, OnHand, Class, Warehouse, Price]• Time[TimeKey, Day_of_Week, Month, Year, JulianDate,

Quarter, etc.]

Replacing OrderDate with Time_key

Tools/Analyze/Tables

Tools/Analyze/Tables

Tools/Analyze/Tables

Tools/Analyze/Documenter

Tools/Analyze/DocumenterCUSTOMER table

http://www.webopedia.comGUID Last modified: Thursday, June 20, 2002 

• Short for Globally Unique Identifier, a unique 128-bit number that is produced by the Windows OS or by some Windows applications to identify a particular component, application, file, database entry, and/or user. For instance, a Web site may generate a GUID and assign it to a user's browser to record and track the session. A GUID is also used in a Windows registry to identify COM DLLs. Knowing where to look in the registry and having the correct GUID yields a lot information about a COM object (i.e., information in the type library, its physical location, etc.). Windows also identifies user accounts by a username (computer/domain and username) and assigns it a GUID. Some database administrators even will use GUIDs as primary key values in databases.

• GUIDs can be created in a number of ways, but usually they are a combination of a few unique settings based on specific point in time (e.g., an IP address, network MAC address, clock date/time, etc.).

Tools/Analyze/DocumenterOrderDetail table

Henry Books ERD (before)

BookInventory

Henry Books ERD (before)

Update Query for Inventory Table[Physical Inventory Date]

Inventory Table: Date Updated

BookInventory Fact TableNote: 2 Time Keys [Pick one]

BookInventory Fact TableNote: 2 Time Keys [Pick one]

BookInventory Fact TableNote: 2 Time Keys [Pick one]

BookInventory Fact TableNote: 2 Time Keys [Pick one]

Henry Books Star Diagram

HB -- Relation List

Fact Table• BookTrans[BookCode, AuthorNum, BranchNum,

Sequence, PubCode, OnHand, InventoryDate]

Dimension Tables• Book[BookCode, Title, Type, Price, Paperback]• Publisher[PubCode, PubName, City, …State, Zip]• Author[AuthorNum, LastName, FirstName, …]• Branch[BranchNum, BranchName, Location, Employees]• Time[TimeKey, Day_of_Week, Month, Year, JulianDate,

Quarter, etc.]

Summary

• Complete Transformations

• How normal are the resulting tables?– 1NF, 2NF, 3NF?

• Document Transformation maps

• Prepare for Appending Tables with new data

• Tools/Analyze/Documenter (next time)