Aggregating Knowledge in a Data Warehouse and Multidimensional AnalysisRafal LukawieckiStrategic Consultant, Project Botticelli Ltdrafal@projectbotticelli.com

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Objectives

• Explain the basics of:1. Data Warehousing2. ETL3. OLAP/Multidimensional Data

• Relate the theory to SQL Server 2008 SSAS and SSIS

This seminar is based on a number of sources including a few dozen of Microsoft-owned presentations, used with permission. Thank you to Marin Bezic, Kathy Sabourin, Aydin Gencler, Bryan Bredehoeft, and Chris Dial for all the support. Thank you to Maciej Pilecki for assistance with demos.

The information herein is for informational purposes only and represents the opinions and views of Project Botticelli and/or Rafal Lukawiecki. The material presented is not certain and may vary based on several factors. Microsoft makes no warranties, express, implied or statutory, as to the information in this presentation.

Portions © 2009 Project Botticelli Ltd & entire material © 2009 Microsoft Corp. Some slides contain quotations from copyrighted materials by other authors, as individually attributed or as already covered by Microsoft Copyright ownerships. All rights reserved. Microsoft, Windows, Windows Vista and other product names are or may be registered trademarks and/or trademarks in the U.S. and/or other countries. The information herein is for informational purposes only and represents the current view of Project Botticelli Ltd as of the date of this presentation.  Because Project Botticelli & Microsoft must respond to changing market conditions, it should not be interpreted to be a commitment on the part of Microsoft, and Microsoft and Project Botticelli cannot guarantee the accuracy of any information provided after the date of this presentation. Project Botticelli makes no warranties, express, implied or statutory, as to the information in this presentation. E&OE.

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1. Data Warehouse (and its relationship to OLAP)

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Let’s Store the Intelligence: DW• SQL Server Analysis Services server is a logical

endpoint for data being aggregated with SSIS• But do not store actual data in it

• Data physically rests in another relational database called a Data Warehouse

• Modelling of data stored in DW and analysed using SSAS is at the heart of good Data Warehouse design

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Star Schema

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Star Schema Benefits

• Transforms normalized data into a simpler model• Delivers high-performance queries• Delivers higher performing queries using Star

Join Query Optimization• Uses mature modeling techniques that are

widely supported by many BI tools• Requires low maintenance as the data

warehouse design evolves

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Snowflake Dimension Tables• Define hierarchies using multiple dimension

tables• Support fact tables with varying granularity• Simplify consolidation of data from multiple

sources

Potential for slower query performance in relational reporting

No difference in performance in Analysis Services database

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OLAP Hierarchies

• Benefits• View of data at different levels of summarization• Path to drill down or drill up

• Implementation• Denormalized DW star

schema dimension• Normalized DW snowflake

dimension• Self-referencing

relationship

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Parent-Child Hierarchy Example

Brian

Amy

Stacia

Stephen

Shu

Michael

Peter

José

Syed

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Fact Table Fundamentals

• Collection of measurements associated with a specific business process

• Specific column types• Foreign keys to dimensions• Measures – numeric and aggregatable• Metadata and lineage

• Consistent granularity – the most atomic level by which the facts can be defined

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Fact Table Examples

Day Grain

Quarter Grain

Reseller sales data by:•Product•Order Date•Reseller•Employee•Sales Territory

Sales quota data by:•Employee•Time

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Date Dimension Table

• Most common dimension used in analysis (aka Time dimension)

• Used consistently with all facts for efficient and flexible analysis

• Useful common attributes – Year, Quarter, Month, Day• Time series analysis support• Navigation and summarization enabled with

hierarchies, such as calendar or fiscal• Single table design (typically not snowflake

design)Tip: Format the key of the dimension as yyyymmdd (e.g. 20060925) to make it readily understandable

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Slowly Changing Dimensions

• Support primary role of data warehouse to describe the past accurately

• Maintain historical context as new or changed data is loaded into dimension tables

• Implement changes by Slowly Changing Dimension (SCD) type• Type 1: Overwrite the existing dimension record• Type 2: Insert a new ‘versioned’ dimension record• Type 3: Track limited history with attributes

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SCD Type 1

• Existing record is updated• History is not preserved

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SCD Type 2

• Existing record is ‘expired’ and new record inserted

• History is preserved• Most common form of SCD

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SCD Type 3

• Existing record is updated• Limited history is preserved• Implementation is rare

SalesTerritoryKey update to 10

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Let’s Get the Data

• We would like to populate facts and dimensions in our Data Warehouse from OLTP data...

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2. Integration and ETL

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Let’s do ETL with SSIS

• SQL Server Integration Services (SSIS) service

• SSIS object model• Two distinct runtime engines:

• Control flow• Data flow

• 32-bit and 64-bit editions

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The Package

• The basic unit of work, deployment, and execution

• An organized collection of:• Connection managers• Control flow components• Data flow components• Variables• Event handlers• Configurations

• Can be designed graphically or built programmatically

• Saved in XML format to the file system or SQL Server

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Control Flow

• Control flow is a process-oriented workflow engine

• A package contains a single control flow• Control flow elements

• Containers• Tasks• Precedence constraints• Variables

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Data Flow

• The Data Flow Task• Performs traditional ETL and more• Fast and scalable

• Data Flow Components• Extract data from Sources• Load data into Destinations• Modify data with Transformations

• Service Paths• Connect data flow components• Create the pipeline

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Row Transformations

• Update column values or create new columns• Transform each row in the pipeline input

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Rowset Transformations• Create new rowsets that can include

• Aggregated values• Sorted values• Sample rowsets• Pivoted or unpivoted rowsets

• This is a heavy-weight performer of SSIS• Are also called asynchronous components

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Split and Join Transformations

• Distribute rows to different outputs• Create copies of the transformation inputs• Join multiple inputs into one output• Perform lookup operations

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Using SQL Server Integration Services for Aggregating and Deriving Data

Demo

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3. OLAP/Multidimensional Data

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SQL Server 2008 Analysis Services

• OLAP component• Aggregates and organizes data from

business data sources• Performs calculations difficult to perform

using relational queries• Supports advanced business intelligence,

such as Key Performance Indicators• Data mining component

• Discovers patterns in both relational and OLAP data

• Enhances the OLAP component with discovered results

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Cube = Unified Dimensional Model• Multidimensional data• Combination of measures and dimensions as

one conceptual model• Measures are sourced from fact tables• Dimensions are sourced from dimension tables

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Dimensions

• Members from tables/views in a data source view (based on a Data Warehouse)

• Contain attributes matching dimension columns• Organize attributes as hierarchies

• One All level and one leaf level• User hierarchies are multi-level combinations of

attributes• Can be placed in display folders

• Used for slicing and dicing by attribute

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Hierarchy

• Defined in Analysis Services• Ordered collection of attributes into levels• Navigation path through dimensional space• Very important to get right!

Customers by Geography

Country

State

City

Customer

Customers by Demographics

Marital

Gender

Customer

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Measure Group

• Group of measures with same dimensionality• Analogous to a fact table• Cube can contain more than one measure group

• E.g. Sales, Inventory, Finance• Defined by dimension relationships

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Sales Inventory Finance

Customers X

Products X X

Time X X X

Promotions X

Warehouse X

Department

X

Account X

Scenario X

Measure Group

Measure GroupD

imen

sio

n

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Dimension Relationships

• Define interaction between dimensions and measure groups

• Relationship types• Regular (a typical dimension)• Fact (Degenerate)• Reference• Many-to-many• Data mining

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Calculations

• Expressions evaluated at query time for values that cannot be stored in fact table

• Types of calculations• Calculated members• Named sets• Scoped assignments

• Calculations are defined using MDX

MDX = MultiDimensional EXpressions

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1. Using BIDS to Review Dimension Design2. Cube Design and Functionality

Demo

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Summary

• As a platform for enterprise Business Intelligence you should consider three things:• A Data Warehouse• Process of Data Integration (incl. ETL)• Multidimensional Analysis (OLAP)

= SQL Server 2008 Engine, SSIS, and SSAS

• Now you can support decision making and performance management through:• Reports, dashboards, Excel integration, data

mining, and better business software

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© 2009 Microsoft Corporation & Project Botticelli Ltd. All rights reserved.

The information herein is for informational purposes only and represents the opinions and views of Project Botticelli and/or Rafal Lukawiecki. The material presented is not certain and may vary based on several factors. Microsoft makes no warranties, express, implied or statutory, as to the information in this presentation.

Portions © 2009 Project Botticelli Ltd & entire material © 2009 Microsoft Corp. Some slides contain quotations from copyrighted materials by other authors, as individually attributed or as already covered by Microsoft Copyright ownerships. All rights reserved. Microsoft, Windows, Windows Vista and other product names are or may be registered trademarks and/or trademarks in the U.S. and/or other countries. The information herein is for informational purposes only and represents the current view of Project Botticelli Ltd as of the date of this presentation.  Because Project Botticelli & Microsoft must respond to changing market conditions, it should not be interpreted to be a commitment on the part of Microsoft, and Microsoft and Project Botticelli cannot guarantee the accuracy of any information provided after the date of this presentation. Project Botticelli makes no warranties, express, implied or statutory, as to the information in this presentation. E&OE.