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Data Analysis Using
SQL and Excel®
Gordon S. Linoff

Wiley Publishing, Inc.

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Data Analysis Using
SQL and Excel®

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Data Analysis Using
SQL and Excel®
Gordon S. Linoff

Wiley Publishing, Inc.

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Data Analysis Using SQL and Excel®
Published by
Wiley Publishing, Inc.
10475 Crosspoint Boulevard
Indianapolis, IN 46256
www.wiley.com

Copyright © 2008 by Wiley Publishing, Inc., Indianapolis, Indiana
Published simultaneously in Canada
ISBN: 978-0-470-09951-3
Manufactured in the United States of America
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Library of Congress Cataloging-in-Publication Data:
Linoff, Gordon.
Data analysis using SQL and Excel / Gordon S. Linoff.
p. cm.
Includes index.
ISBN 978-0-470-09951-3 (paper/website)
1. SQL (Computer program language) 2. Querying (Computer science) 3. Data mining. 4.
Microsoft Excel (Computer file) I. Title.
QA76.73.S67L56 2007
005.75'85--dc22
2007026313
Trademarks: Wiley, the Wiley logo, and related trade dress are trademarks or registered trademarks
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To Giuseppe for sixteen years, five books, and counting . . .

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About the Author

Gordon Linoff (gordon@data-miners.com) is a recognized expert in the field
of data mining. He has more than twenty-five years of experience working
with companies large and small to analyze customer data and to help design
data warehouses. His passion for SQL and relational databases dates to the
early 1990s, when he was building a relational database engine designed for
large corporate data warehouses at the now-defunct Thinking Machines Corporation. Since then, he has had the opportunity to work with all the leading
database vendors, including Microsoft, Oracle, and IBM.
With his colleague Michael Berry, Gordon has written three of the most popular books on data mining, starting with Data Mining Techniques for Marketing,
Sales, and Customer Support. In addition to writing books on data mining, he
also teaches courses on data mining, and has taught thousands of students on
four continents.
Gordon is currently a principal at Data Miners, a consulting company he
and Michael Berry founded in 1998. Data Miners is devoted to doing and
teaching data mining and customer-centric data analysis.

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Credits

Acquisitions Editor
Robert Elliott

Vice President and Executive
Publisher
Joseph B. Wikert

Development Editor
Ed Connor

Project Coordinator, Cover
Lynsey Osborn

Technical Editor
Michael J. A. Berry

Copy Editor
Kim Cofer

Graphics and Production
Specialists
Craig Woods, Happenstance
Type-O-Rama
Oso Rey, Happenstance
Type-O-Rama

Editorial Manager
Mary Beth Wakefield

Proofreading
Ian Golder, Word One

Production Manager
Tim Tate

Indexing
Johnna VanHoose Dinse

Vice President and Executive
Group Publisher
Richard Swadley

Anniversary Logo Design
Richard Pacifico

Production Editor
William A. Barton

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Contents

Foreword

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Acknowledgments

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Introduction
Chapter 1

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A Data Miner Looks at SQL
Picturing the Structure of the Data
What Is a Data Model?
What Is a Table?
Allowing NULL Values
Column Types
What Is an Entity-Relationship Diagram?
The Zip Code Tables
Subscription Dataset
Purchases Dataset

Picturing Data Analysis Using Dataflows
What Is a Dataflow?
Dataflow Nodes (Operators)
READ: Reading a Database Table
OUTPUT: Outputting a Table (or Chart)
SELECT: Selecting Various Columns in the Table
FILTER: Filtering Rows Based on a Condition
APPEND: Appending New Calculated Columns
UNION: Combining Multiple Datasets into One
AGGREGATE: Aggregating Values
LOOKUP: Looking Up Values in One Table in Another
CROSSJOIN: General Join of Two Tables
JOIN: Join Two Tables Together Using a Key Column
SORT: Ordering the Results of a Dataset
Dataflows, SQL, and Relational Algebra

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SQL Queries

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What to Do, Not How to Do It
A Basic SQL Query
A Basic Summary SQL Query
What it Means to Join Tables
Cross-Joins: The Most General Joins
Lookup: A Useful Join
Equijoins
Nonequijoins
Outer Joins
Other Important Capabilities in SQL
UNION ALL
CASE
IN

Subqueries Are Our Friend
Subqueries for Naming Variables
Subqueries for Handling Summaries
Subqueries and IN
Rewriting the “IN” as a JOIN
Correlated Subqueries
The NOT IN Operator
Subqueries for UNION ALL

Chapter 2

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Lessons Learned

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What’s In a Table? Getting Started with Data Exploration
What Is Data Exploration?
Excel for Charting

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A Basic Chart: Column Charts
Inserting the Data
Creating the Column Chart
Formatting the Column Chart
Useful Variations on the Column Chart
A New Query
Side-by-Side Columns
Stacked Columns
Stacked and Normalized Columns
Number of Orders and Revenue
Other Types of Charts
Line Charts
Area Charts
X-Y Charts (Scatter Plots)

What Values Are in the Columns?
Histograms
Histograms of Counts
Cumulative Histograms of Counts
Histograms (Frequencies) for Numeric Values
Ranges Based on the Number of Digits, Using
Numeric Techniques

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Ranges Based on the Number of Digits, Using
String Techniques
More Refined Ranges: First Digit Plus Number of Digits
Breaking Numerics into Equal-Sized Groups

More Values to Explore — Min, Max, and Mode

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Minimum and Maximum Values
The Most Common Value (Mode)
Calculating Mode Using Standard SQL
Calculating Mode Using SQL Extensions
Calculating Mode Using String Operations

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Exploring String Values
Histogram of Length
Strings Starting or Ending with Spaces
Handling Upper- and Lowercase
What Characters Are in a String?

Exploring Values in Two Columns
What Are Average Sales By State?
How Often Are Products Repeated within a Single Order?
Direct Counting Approach
Comparison of Distinct Counts to Overall Counts
Which State Has the Most American Express Users?

From Summarizing One Column to Summarizing
All Columns
Good Summary for One Column
Query to Get All Columns in a Table
Using SQL to Generate Summary Code

Chapter 3

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Lessons Learned

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How Different Is Different?
Basic Statistical Concepts

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The Null Hypothesis
Confidence and Probability
Normal Distribution

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How Different Are the Averages?
The Approach
Standard Deviation for Subset Averages
Three Approaches
Estimation Based on Two Samples
Estimation Based on Difference

Counting Possibilities
How Many Men?
How Many Californians?
Null Hypothesis and Confidence
How Many Customers Are Still Active?
Given the Count, What Is the Probability?
Given the Probability, What Is the Number of Stops?
The Rate or the Number?

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Ratios, and Their Statistics
Standard Error of a Proportion
Confidence Interval on Proportions
Difference of Proportions
Conservative Lower Bounds

Chi-Square

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Expected Values
Chi-Square Calculation
Chi-Square Distribution
Chi-Square in SQL
What States Have Unusual Affinities for Which
Types of Products?
Data Investigation
SQL to Calculate Chi-Square Values
Affinity Results

Chapter 4

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Lessons Learned

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Where Is It All Happening? Location, Location, Location
Latitude and Longitude

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Definition of Latitude and Longitude
Degrees, Minutes, Seconds, and All That
Distance between Two Locations
Euclidian Method
Accurate Method
Finding All Zip Codes within a Given Distance
Finding Nearest Zip Code in Excel
Pictures with Zip Codes
The Scatter Plot Map
Who Uses Solar Power for Heating?
Where Are the Customers?

Census Demographics
The Extremes: Richest and Poorest
Median Income
Proportion of Wealthy and Poor
Income Similarity and Dissimilarity Using Chi-Square
Comparison of Zip Codes with and without Orders
Zip Codes Not in Census File
Profiles of Zip Codes with and without Orders
Classifying and Comparing Zip Codes

Geographic Hierarchies
Wealthiest Zip Code in a State?
Zip Code with the Most Orders in Each State
Interesting Hierarchies in Geographic Data
Counties
Designated Marketing Areas (DMAs)
Census Hierarchies
Other Geographic Subdivisions

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Calculating County Wealth
Identifying Counties
Measuring Wealth
Distribution of Values of Wealth
Which Zip Code Is Wealthiest Relative to Its County?
County with Highest Relative Order Penetration

Mapping in Excel
Why Create Maps?
It Can’t Be Done
Mapping on the Web
State Boundaries on Scatter Plots of Zip Codes
Plotting State Boundaries
Pictures of State Boundaries

Chapter 5

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Lessons Learned

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It’s a Matter of Time
Dates and Times in Databases

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Some Fundamentals of Dates and Times in Databases
Extracting Components of Dates and Times
Converting to Standard Formats
Intervals (Durations)
Time Zones
Calendar Table

Starting to Investigate Dates
Verifying that Dates Have No Times
Comparing Counts by Date
Orderlines Shipped and Billed
Customers Shipped and Billed
Number of Different Bill and Ship Dates per Order
Counts of Orders and Order Sizes
Items as Measured by Number of Units
Items as Measured by Distinct Products
Size as Measured by Dollars
Days of the Week
Billing Date by Day of the Week
Changes in Day of the Week by Year
Comparison of Days of the Week for Two Dates

How Long between Two Dates?
Duration in Days
Duration in Weeks
Duration in Months
How Many Mondays?
A Business Problem about Days of the Week
Outline of a Solution
Solving It in SQL
Using a Calendar Table Instead

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Year-over-Year Comparisons
Comparisons by Day
Adding a Moving Average Trend Line
Comparisons by Week
Comparisons by Month
Month-to-Date Comparison
Extrapolation by Days in Month
Estimation Based on Day of Week
Estimation Based on Previous Year

Counting Active Customers by Day
How Many Customers on a Given Day?
How Many Customers Every Day?
How Many Customers of Different Types?
How Many Customers by Tenure Segment?

Simple Chart Animation in Excel
Order Date to Ship Date
Order Date to Ship Date by Year
Querying the Data
Creating the One-Year Excel Table
Creating and Customizing the Chart

Chapter 6

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Lessons Learned

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How Long Will Customers Last? Survival Analysis
to Understand Customers and Their Value
Background on Survival Analysis

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Life Expectancy
Medical Research
Examples of Hazards

The Hazard Calculation
Data Investigation
Stop Flag
Tenure
Hazard Probability
Visualizing Customers: Time versus Tenure
Censoring

Survival and Retention
Point Estimate for Survival
Calculating Survival for All Tenures
Calculating Survival in SQL
Step 1. Create the Survival Table
Step 2: Load POPT and STOPT
Step 3: Calculate Cumulative Population
Step 4: Calculate the Hazard
Step 5: Calculate the Survival
Step 6: Fix ENDTENURE and NUMDAYS in Last Row
Generalizing the SQL

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A Simple Customer Retention Calculation
Comparison between Retention and Survival
Simple Example of Hazard and Survival
Constant Hazard
What Happens to a Mixture
Constant Hazard Corresponding to Survival

Comparing Different Groups of Customers

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Summarizing the Markets
Stratifying by Market
Survival Ratio
Conditional Survival

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Comparing Survival over Time

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How Has a Particular Hazard Changed over Time?
What Is Customer Survival by Year of Start?
What Did Survival Look Like in the Past?

Important Measures Derived from Survival
Point Estimate of Survival
Median Customer Tenure
Average Customer Lifetime
Confidence in the Hazards

Using Survival for Customer Value Calculations
Estimated Revenue
Estimating Future Revenue for One Future Start
SQL Day-by-Day Approach
SQL Summary Approach
Estimated Revenue for a Simple Group of Existing Customers
Estimated Second Year Revenue for a Homogenous Group
Pre-calculating Yearly Revenue by Tenure
Estimated Future Revenue for All Customers

Chapter 7

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Lessons Learned

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Factors Affecting Survival: The What and
Why of Customer Tenure
What Factors Are Important and When

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Explanation of the Approach
Using Averages to Compare Numeric Variables
The Answer
Answering the Question in SQL
Extension to Include Confidence Bounds
Hazard Ratios
Interpreting Hazard Ratios
Calculating Hazard Ratios
Why the Hazard Ratio

Left Truncation
Recognizing Left Truncation
Effect of Left Truncation

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How to Fix Left Truncation, Conceptually
Estimating Hazard Probability for One Tenure
Estimating Hazard Probabilities for All Tenures

Time Windowing

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A Business Problem
Time Windows = Left Truncation + Right Censoring
Calculating One Hazard Probability Using a Time Window
All Hazard Probabilities for a Time Window
Comparison of Hazards by Stops in Year

Competing Risks

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Examples of Competing Risks
I=Involuntary Churn
V=Voluntary Churn
M=Migration
Other
Competing Risk “Hazard Probability”
Competing Risk “Survival”
What Happens to Customers over Time
Example
A Cohort-Based Approach
The Survival Analysis Approach

Before and After

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Three Scenarios
A Billing Mistake
A Loyalty Program
Raising Prices
Using Survival Forecasts
Forecasting Identified Customers Who Stopped
Estimating Excess Stops
Before and After Comparison
Cohort-Based Approach
Direct Estimation of Event Effect
Approach to the Calculation
Time-Varying Covariate Survival Using SQL and Excel

Chapter 8

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Lessons Learned

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Customer Purchases and Other Repeated Events
Identifying Customers

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Who Is the Customer?
How Many?
How Many Genders in a Household
Investigating First Names
Other Customer Information
First and Last Names
Addresses
Other Identifying Information

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How Many New Customers Appear Each Year?
Counting Customers
Span of Time Making Purchases
Average Time between Orders
Purchase Intervals

RFM Analysis

370

The Dimensions
Recency
Frequency
Monetary
Calculating the RFM Cell
Utility of RFM
A Methodology for Marketing Experiments
Customer Migration
RFM Limits

Which Households Are Increasing Purchase
Amounts Over Time?
Comparison of Earliest and Latest Values
Calculating the Earliest and Latest Values
Comparing the First and Last Values
Comparison of First Year Values and Last Year Values
Trend from the Best Fit Line
Using the Slope
Calculating the Slope

Time to Next Event
Idea behind the Calculation
Calculating Next Purchase Date Using SQL
From Next Purchase Date to Time-to-Event
Stratifying Time-to-Event

Chapter 9

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Lessons Learned

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What’s in a Shopping Cart? Market Basket Analysis
and Association Rules
Exploratory Market Basket Analysis

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Scatter Plot of Products
Duplicate Products in Orders
Histogram of Number of Units
Products Associated with One-Time Customers
Products Associated with the Best Customers
Changes in Price

Combinations (Item Sets)
Combinations of Two Products
Number of Two-Way Combinations
Generating All Two-Way Combinations
Examples of Combinations
Variations on Combinations
Combinations of Product Groups
Multi-Way Combinations

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Households Not Orders
Combinations within a Household
Investigating Products within Households but
Not within Orders
Multiple Purchases of the Same Product

The Simplest Association Rules
Associations and Rules
Zero-Way Association Rules
What Is the Distribution of Probabilities?
What Do Zero-Way Associations Tell Us?

One-Way Association Rules
Example of One-Way Association Rules
Generating All One-Way Rules
One-Way Rules with Evaluation Information
One-Way Rules on Product Groups
Calculating Product Group Rules Using an
Intermediate Table
Calculating Product Group Rules Using
Window Functions

Two-Way Associations
Calculating Two-Way Associations
Using Chi-Square to Find the Best Rules
Applying Chi-Square to Rules
Applying Chi-Square to Rules in SQL
Comparing Chi-Square Rules to Lift
Chi-Square for Negative Rules
Heterogeneous Associations
Rules of the Form “State Plus Product”
Rules Mixing Different Types of Products

Extending Association Rules
Multi-Way Associations
Rules Using Attributes of Products
Rules with Different Left- and Right-Hand Sides
Before and After: Sequential Associations

Lessons Learned

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Chapter 10 Data Mining Models in SQL
Introduction to Directed Data Mining
Directed Models
The Data in Modeling
Model Set
Score Set
Prediction Model Sets versus Profiling Model Sets
Examples of Modeling Tasks
Similarity Models
Yes-or-No Models (Binary Response Classification)

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Yes-or-No Models with Propensity Scores
Multiple Categories
Estimating Numeric Values
Model Evaluation

Look-Alike Models

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What Is the Model?
What Is the Best Zip Code?
A Basic Look-Alike Model
Look-Alike Using Z-Scores
Example of Nearest Neighbor Model

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Lookup Model for Most Popular Product

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Most Popular Product
Calculating Most Popular Product Group
Evaluating the Lookup Model
Using a Profiling Lookup Model for Prediction
Using Binary Classification Instead

Lookup Model for Order Size
Most Basic Example: No Dimensions
Adding One Dimension
Adding More Dimensions
Examining Nonstationarity
Evaluating the Model Using an Average Value Chart

Lookup Model for Probability of Response
The Overall Probability as a Model
Exploring Different Dimensions
How Accurate Are the Models?
Adding More Dimensions

Naïve Bayesian Models (Evidence Models)
Some Ideas in Probability
Probabilities
Odds
Likelihood
Calculating the Naïve Bayesian Model
An Intriguing Observation
Bayesian Model of One Variable
Bayesian Model of One Variable in SQL
The “Naïve” Generalization
Naïve Bayesian Model: Scoring and Lift
Scoring with More Attributes
Creating a Cumulative Gains Chart
Comparison of Naïve Bayesian and Lookup Models

Lessons Learned
Chapter 11 The Best-Fit Line: Linear Regression Models
The Best-Fit Line
Tenure and Amount Paid

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Properties of the Best-fit Line
What Does Best-Fit Mean?
Formula for Line
Expected Value
Error (Residuals)
Preserving the Averages
Inverse Model
Beware of the Data
Trend Lines in Charts
Best-fit Line in Scatter Plots
Logarithmic, Power, and Exponential Trend Curves
Polynomial Trend Curves
Moving Average
Best-fit Using LINEST() Function
Returning Values in Multiple Cells
Calculating Expected Values
LINEST() for Logarithmic, Exponential, and Power Curves

Measuring Goodness of Fit Using R2
The R2 Value
Limitations of R2
What R2 Really Means

Direct Calculation of Best-Fit Line Coefficients
Doing the Calculation
Calculating the Best-Fit Line in SQL
Price Elasticity
Price Frequency
Price Frequency for $20 Books
Price Elasticity Model in SQL
Price Elasticity Average Value Chart

Weighted Linear Regression
Customer Stops during the First Year
Weighted Best Fit
Weighted Best-Fit Line in a Chart
Weighted Best-Fit in SQL
Weighted Best-Fit Using Solver
The Weighted Best-Fit Line
Solver Is Better Than Guessing

More Than One Input Variable
Multiple Regression in Excel
Getting the Data
Investigating Each Variable Separately
Building a Model with Three Input Variables
Using Solver for Multiple Regression
Choosing Input Variables One-By-One
Multiple Regression in SQL

Lessons Learned

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513
515
515
517
518
518
519
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521
522
524
525
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528
530
531

532
532
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Contents
Chapter 12 Building Customer Signatures for Further Analysis
What Is a Customer Signature?

563
564

What Is a Customer?
Sources of Data for the Customer Signature
Current Customer Snapshot
Initial Customer Information
Self-Reported Information
External Data (Demographic and So On)
About Their Neighbors
Transaction Summaries
Using Customer Signatures
Predictive and Profile Modeling
Ad Hoc Analysis
Repository of Customer-Centric Business Metrics

565
566
566
567
568
568
569
569
570
570
570
570

Designing Customer Signatures

571

Column Roles
Identification Columns
Input Columns
Target Columns
Foreign Key Columns
Cutoff Date
Profiling versus Prediction
Time Frames
Naming of Columns
Eliminating Seasonality
Adding Seasonality Back In
Multiple Time Frames

571
571
572
572
572
573
573
573
574
574
575
576

Operations to Build a Customer Signature
Driving Table
Using an Existing Table as the Driving Table
Derived Table as the Driving Table
Looking Up Data
Fixed Lookup Tables
Customer Dimension Lookup Tables
Initial Transaction
Without Window Functions
With Window Functions
Pivoting
Payment Type Pivot
Channel Pivot
Year Pivot
Order Line Information Pivot
Summarizing
Basic Summaries
More Complex Summaries

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Extracting Features

596

Geographic Location Information
Date Time Columns
Patterns in Strings
Email Addresses
Addresses
Product Descriptions
Credit Card Numbers

596
597
598
598
599
599
600

Summarizing Customer Behaviors

601

Calculating Slope for Time Series
Calculating Slope from Pivoted Time Series
Calculating Slope for a Regular Time Series
Calculating Slope for an Irregular Time Series
Weekend Shoppers
Declining Usage Behavior

Appendix

601
601
603
604
604
606

Lessons Learned

609

Equivalent Constructs Among Databases
String Functions

611
612

Searching for Position of One String within Another
IBM
Microsoft
mysql
Oracle
SAS proc sql
String Concatenation
IBM
Microsoft
mysql
Oracle
SAS proc sql
String Length Function
IBM
Microsoft
mysql
Oracle
SAS proc sql
Substring Function
IBM
Microsoft
mysql
Oracle
SAS proc sql
Replace One Substring with Another
IBM
Microsoft

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