The Language of SQL- P46 docx

Rather than viewing a static crosstab report, the user can modify the pivot table quickly by rearranging data elements into the various areas: rows, columns, and data.. In addition, pivo

However, the pivot table also adds some key elements that greatly enhance its

usefulness:

■ First, a pivot table is completely interactive Rather than viewing a static

crosstab report, the user can modify the pivot table quickly by rearranging

data elements into the various areas: rows, columns, and data In addition,

pivot tables provide a fourth data area called the page, which allows for data

items to be used in filtering but not displayed

■ The data in pivot tables exists as a separate store of data and can even be

saved as a separate file Because the data in a pivot table exists on its own,

users can rearrange the data without affecting the data from which the pivot

table was created

■ Pivot tables allow for additional data selection For example, specific

values of various data items can be excluded Or the aggregated values in

the data area of the pivot table can be changed from sums to counts

■ Pivot tables can add drill-down functionality to the data For example,

if the underlying data contains columns such as country, state, and city, the

pivot table can be set up so you can double-click on a country to see all

states in that country and then double-click again to see all cities in each

state

■ Pivot tables allow users to drill through from summarized data to the

underlying details Thus, you have the ability to double-click on any

individual value in the data area to see the individual rows that contributed

to that number

It’s beyond the scope of this book to explore pivot tables in any amount of detail

But an awareness of what you can accomplish with pivot tables can be very useful

for the SQL developer

Figure 20.3 shows an example of a pivot table that was created from the same

data as listed earlier, but with the addition of two new columns: Date and

Subcategory The Subcategory column is a further breakdown of the product

category In this pivot table, the date, product category, and subcategory were all

put in the rows area This illustrates how pivot tables can provide a further

breakdown of data in a very flexible manner

Spreadsheets and Pivot Tables 211

Figure 20.3

Pivot table.

The important point about this pivot table is that there are three different levels

of groups in the rows First, it divides all data by date, then by product category, and finally by subcategory You can see that on 12/5/09, there were two different product categories sold: chairs and paper For chairs, there were two different subcategories sold: metal and plastic For each of these categories, the pivot table provides a breakdown of sales by customer

As such, pivot tables are very adept at summarizing data in innumerable ways Additionally, users have the ability to arrange data items in almost any desired format

Looking Ahead

In this chapter, we’ve examined a few ways in which reporting tools and spread-sheets can be used to display data in custom formats In particular, the crosstab report adds an ability to summarize data in a way that is difficult to present strictly through SQL statements Pivot tables in Excel utilize the basic concept of the crosstab report and extend it to provide additional flexibility and functionality for users By being aware of reporting and user tools available to reformat data, SQL developers can focus their talents more productively on retrieving data and let the reporting tool or user handle more complex display issues

Now that you’ve completed the book, why not try out a few commands on your own? If you haven’t already done so, take a look at Appendices A, B, and C to get some tips on how to get started with Microsoft SQL Server, MySQL, or Oracle These appendices provide instructions on how to install the free versions of these databases, and they also provide some basic information on how to use the software to execute SQL commands

Finally, I sincerely hope that this book has served as a useful guide into the world

of SQL At the start of the book, I mentioned that SQL involves both logic and

Chapter 20 ■ Strategies for Displaying Data

212

language The language component is fairly obvious In each chapter, I’ve

stres-sed the keywords that are introduced and the meaning behind those words But

now that you’ve completed the book, I hope you can appreciate that the power of

SQL is with the logic that it encompasses

It is pure logic that allows you take a bunch of values arranged in columns and

rows and transform it into something approaching information The challenge

in using SQL is in determining how to apply logic to real-world data This is

where the theoretical and practical meet In using functions, aggregation, joins,

subqueries, views, and the like, you’ll grapple with the reality of raw data and

learn how to manipulate it with a few twists of logic

But logic isn’t the end of the matter The language of SQL plays an equally

important role I would say that the real beauty of SQL lies in the fact that the

language is quite sparse It’s neither cryptic nor verbose Each keyword has a

distinct purpose and specifies a particular bit of logic and nothing more I

wouldn’t go so far as to say that SQL has poetic qualities, but within the realm of

computer languages, the language has a certain aesthetic appeal

Looking Ahead 213

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appendix A

Getting Started

with Microsoft

SQL Server

Overview

The procedure to install the free version of Microsoft SQL Server is as follows This procedure was tested on a PC with the Windows 7 operating system Please note that the specific instructions may vary from what is shown here, depending

on what is already installed on your PC

As these procedures may change over time, please consult www.courseptr.com/ downloads for any updates

There are two main steps involved:

■ Install SQL Server Express 2008

■ Install SQL Server Management Studio

Microsoft SQL Server Express 2008 allows you to create databases The SQL Server Management Studio is a graphical interface that allows you to issue SQL commands to interact with the server and any databases you create

Both downloads are available at www.microsoft.com/sqlserver

Installing SQL Server Express 2008

The steps for installing the Microsoft SQL Server database are as follows

1 Go to www.microsoft.com/sqlserver

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