HP Intelligent Management Center Standard Software Platform - Manual (Page 663)

Amount Customer Order#
7911.80 SFB Inc. 10495
1956.20 La Bomba de Bicicleta 10501
1683.60 BG Mountain Inc. 10511
19766.20 Sierra Bicycle Group 10544
29759.55 Mountain Tops Inc. 10568
12763.95 Sierra Bicycle Group 10579
The information in this table is organized according to the Order# field. This
is fine anytime you want to look up information in the table based on order
numbers. However, what if you want to look up information specific to a
certain customer?
Say you want to look up all orders made by Sierra Bicycle Group. The
database engine must begin by looking at the first order number in the list
and checking to see if the customer name matches the request. If not, it goes
to the second order number, and checks that customer name. When an order
number is reached that contains the correct customer name, the database
engine retrieves the information, then continues to the next order number.
Using this technique, both the Order# field and the Customer field must be
read for every single record in the table. This takes a long time and a large
amount of computer processing effort for examining extensive database
tables with thousands, or even millions of records.
Instead, you can create an index for the table based on the Customer field.
Such an index might look like this:
Crystal Reports 2008 SP3 User's Guide 663
25 Understanding Databases
Databases overview