Pivot Table 概念介绍

 

Excel Pivot Table Fundamentals

I won't try and hide the fact from you that I am a big fan of Pivot Tables. I use them a lot in the development of Spreadsheets for my clients. Once the client sees the Pivot Table, they nearly always ask "could I do that?" the answer of course is yes! Unfortunately most people tend to shy away from Pivot Tables, as they see them as too complex. to be honest with you, when you first use a Pivot Table the whole thing can seem a bit daunting. Don't be put off by this as persistence will almost certainly pay off. I find the best part about Pivot Tables is their ability to be manipulated via 'Trial-and-Error' and immediately show the result. If its' not what you expect, simply use the Undo feature and/or have another go!  What you must always remember is that you are not changing the structure of your original table in anyway at all, so you can do no harm!

Why are they called Pivot Tables ? - Well, basically they allow us to pivot our data via drag-and-drop to produce meaningful information. This makes Pivot Tables interactive in that once the table is complete we can very easily see what effect moving (or pivoting) our data has on our information. This will become patently clear once you give Pivot Tables a go. Believe me, no matter how experienced you get at Pivot Tables there will always be an element of trial-and-error involved in producing the desired results! What this means is you will find yourself pivoting your table a lot!

What would we use them for ? - We would use a Pivot Table to produce meaningful information from a table of information.  Imagine you have a table of data that contains names, addresses, ages, occupations, phone numbers, postcodes etc.  With a Pivot Table we could very easily and quickly find out:

1. How many people have the same names.

2. How many postcodes are the same.

3. A count of a particular occupation.

4. See only people that match a particular occupation.

5. Find out the addresses of people that match a postcode

In fact the list can go on and on!

What is the advantage ? - Perhaps the biggest advantage to using Pivot Tables is the fact that we can generate and extract meaningful information from a large table of information within a matter of minutes. Or perhaps it is because they will not use up a lot of memory from your PC. In a lot of cases we could get the same results from a table of data by using Excels built in functions, but this would take more time and use far more memory. On top of this, if we wanted some new information we can simply drag-and-drop (pivot). We can also opt to have our information update each time we open the Workbook and/or by clicking refresh.

Pivot Charts - In Excel 2000 Microsoft introduced Pivot Charts. These are simply charts that are read from the table created via the Pivot Table Wizard. In fact Pivot Tables are really no longer just Pivot Tables, they are now PivotTables and PivotChart Reports. These two features go hand-in-hand with each other. By this I mean, when you create a Pivot Table you can also create a Pivot Chart at the same time with no extra effort needed on your part. Pivot Charts allow us to create professional interactive charts that were previously not possible without either VBA or using Excel's Controls.

Tables and Lists Guidelines for Pivot Tables

The most important factors when considering using a Pivot Table is to have our data set up in what could be termed as a table and/or list.  As our Pivot Table will be basing all its data on this list or table it is vital that we set our tables and lists up in a uniform way.

In the context we are discussing here, a Table is no more than a List (with a heading) with more than one Column of data and a different heading for each column.  A List is often referred to in the context of a Table as well. The 'good practice' that applies to setting up a List will aid us greatly when we need to apply a Pivot Table to our Data. When we extract data via the use of Lookup functions or Database functions we can be a little less stringent in how we set up our Table or List. This is because we can always compensate with the aid of a function and probably still get our result. However, having said this we should always set up our List or Table as well as possible. When we use Excels built-in features they will and do assume a lot about the layout and setting up of your data. They do have a degree of flexibility but more often than not you will find it easier to follow the guidelines for setting up your Table or List.

Let's look at what I believe to be the most important aspects of setting up a Table or List. 

1. Headings. This is a must! They should always be in the row directly above your data. Never have a blank row between your data and the headings. Make them distinct in some way eg; Bold them.

2. Leave at least three blank rows above your headings. These can be used for formulas, critical data etc. You can hide the Rows if you wish. 

3. If you do have more than one List or Table on the same Worksheet leave at least one blank column between your List and Tables. This will aid Excel in recognizing them as separate. However, if the lists and tables are related to each other make them into one large table.

4. Avoid blank cells within your data.  Rather than leaving blanks for the same data in a column repeat the data as many times as needed.

5. Sort your List or Data, preferably by the left most column. This in not so much for Pivot Tables, but for the person reading the data.