Datasheet

ManualsBrandsFor Dummies Manualsbooks978-0-470-40747-9

Chapter 1

What’s in a Data Warehouse?

In This Chapter

▶ Understanding what a data warehouse is and what it does

▶ Looking at the history of data warehousing

▶ Differentiating between bigger and better

▶ Grasping the historical perspective of a data warehouse

▶ Ensuring that your data warehouse isn’t a data dump

f you gather 100 computer consultants experienced in data warehousing

in a room and give them this single-question written quiz, “Define a

data warehouse in 20 words or fewer,” at least 95 of the consultants will turn

in their paper with a one- or two-sentence definition that includes the terms

subject-oriented, time-variant, and read-only. The other five consultants’

replies will likely focus more on business than on technology and use a

phrase such as “improve corporate decision-making through more timely

access to information.”

Forget all that. The following section gives you a no-nonsense definition

guaranteed to be free of both technical and business-school jargon.

Throughout the rest of the chapter, I assist you in better understanding

data warehousing from its history and overall value to your business.

The Data Warehouse: A Place

for Your Data Assets

A data warehouse is a home for your high-value data, or data assets, that

originates in other corporate applications, such as the one your company

uses to fill customer orders for its products, or some data source external

to your company, such as a public database that contains sales information

gathered from all your competitors.

05_407479-ch01.indd 905_407479-ch01.indd 9 1/26/09 7:23:41 PM1/26/09 7:23:41 PM

COPYRIGHTED MATERIAL

Summary of content (16 pages)

PAGE 1
Chapter 1 In This Chapter RI ▶ Understanding what a data warehouse is and what it does AL What’s in a Data Warehouse? ▶ Looking at the history of data warehousing TE ▶ Differentiating between bigger and better ▶ Grasping the historical perspective of a data warehouse MA ▶ Ensuring that your data warehouse isn’t a data dump D I RI GH TE f you gather 100 computer consultants experienced in data warehousing in a room and give them this single-question written quiz, “Define a data warehouse in 2
PAGE 2
10 Part I: The Data Warehouse: Home for Your Data Assets If your company’s data warehouse were advertised as a product for sale, it might be described this way: “Contains high-quality, refined and purified information, all of which has undergone a 25-point quality check and is offered to you with a warranty to guarantee hassle-free ownership so that you can better monitor the performance of your business.
PAGE 3
Chapter 1: What’s in a Data Warehouse? 2. The team in charge of building the data warehouse assigns a group of business users and other key individuals within the company to play the role of subject-matter experts. Together, the data warehousing team and subject-matter experts compile a list of different types of information that can enable them to use the data warehouse to help track sales activity (or whatever the focus is for the project). 3.
PAGE 4
12 Part I: The Data Warehouse: Home for Your Data Assets Run the business Place an order Figure 1-1: Most computer applications create data as a result of an activity or transaction; a data warehouse instead swipes data created elsewhere and converts it into information.
PAGE 5
Chapter 1: What’s in a Data Warehouse? ✓ Data: Facts and information about something ✓ Warehouse: A location or facility for storing goods and merchandise Today’s data warehousing defined Data warehousing is the coordinated, architected, and periodic copying of data from various sources, both inside and outside the enterprise, into an environment optimized for analytical and informational processing.
PAGE 6
14 Part I: The Data Warehouse: Home for Your Data Assets The key concept in this definition is that a data warehouse breaks down the barriers created by non-enterprise, process-focused applications and consolidates information into a single view for users to access.
PAGE 7
Chapter 1: What’s in a Data Warehouse? The 1970s — the preparation The 1970s: Disco and leisure suits were in. And the computing world was dominated by the mainframe. Real data-processing applications, the ones run on the corporate mainframe, almost always had a complicated set of files or early-generation databases (not the table-oriented relational databases most applications use today) in which they stored data.
PAGE 8
16 Part I: The Data Warehouse: Home for Your Data Assets Additionally, commercial and hardware/software companies began to emerge with solutions to this problem. Between 1976 and 1979, the concept for a new company, Teradata, grew out of research at the California Institute of Technology (Caltech), driven from discussions with Citibank’s advanced technology group. Founders worked to design a database management system for parallel processing with multiple microprocessors, specifically for decision support.
PAGE 9
Chapter 1: What’s in a Data Warehouse? of their product, and in 1986, Fortune magazine named Teradata Product of the Year. Teradata, still in existence today, built the first data warehousing appliance — a combination of hardware and software to solve the data warehousing needs of many. Other companies began to formulate their strategies, as well.
PAGE 10
18 Part I: The Data Warehouse: Home for Your Data Assets accessing data directly from the files and databases didn’t work, the 1990s philosophy involved going back to the 1970s method, in which data from those places was copied to another location — only doing it right this time. And data warehousing was born. In 1993, Bill Inmon wrote Building the Data Warehouse (Wiley). Many people recognize Bill as the Father of Data Warehousing.
PAGE 11
Chapter 1: What’s in a Data Warehouse? Although the vendor community has consolidated, innovation hasn’t ceased. More cost-effective solutions have emerged, led by Microsoft enabling small and mid-sized businesses to implement data warehousing solutions. Additionally, less expensive alternatives are emerging from a new set of vendors, those within the open source community, including vendors such as Pentaho and Jaspersoft.
PAGE 12
20 Part I: The Data Warehouse: Home for Your Data Assets To determine the size you need for your data warehouse, follow these steps: 1. Determine the mission, or the business objectives, of the data warehouse. Ask the question, “Why bother creating this warehouse?” 2. Determine the functionality that you want the data warehouse to have. Figure out what types of questions users will ask. 3. Determine what contents (types of data) the data warehouse needs to support its functionality.
PAGE 13
Chapter 1: What’s in a Data Warehouse? placed 1 Orders during store West Store Central Store East Store hours (9-5) for each 2 Data transaction (order) is stored in the application database Figure 1-2: Because you bulkload data into a data warehouse, the time delay gives you a historical perspective.
PAGE 14
22 Part I: The Data Warehouse: Home for Your Data Assets this story is usually mistaken as, “Put as much data as possible in the warehouse.” In reality, the data warehouse just described was probably one that focused exclusively on sales activity. Remember that although disposable diapers and beer are dramatically different products, they’re both members of the same type of data (retail products).
PAGE 15
Chapter 1: What’s in a Data Warehouse? Figure 1-4 shows one possible environment for your data warehouse if you pursue the philosophy of “Go get everything you possibly can,” or what I call the data dump approach.
PAGE 16
24 Part I: The Data Warehouse: Home for Your Data Assets