Datasheet

16
Part I: Basic Concepts
Figure 1-3:
Each data-
base row
contains
a record;
each
database
column
holds a
single
attribute.
ColumnsRow
Enjoy the view
One of my favorite views is of the Yosemite Valley from the mouth of the
Wawona Tunnel, late on a spring afternoon. Golden light bathes the sheer
face of El Capitan, Half Dome glistens in the distance, and Bridal Veil Falls
forms a silver cascade of sparkling water, while a trace of wispy clouds
weaves a tapestry across the sky. Databases have views as well — even if
they’re not quite that picturesque. The beauty of database views is their
sheer usefulness when you’re working with your data.
Tables can contain many columns and rows. Sometimes all that data
interests you, and sometimes it doesn’t. Only some columns of a table may
interest you, or perhaps you want to see only rows that satisfy a certain
condition. Some columns of one table and some other columns of a related
table may interest you. To eliminate data that isn’t relevant to your current
needs, you can create a view — a subset of a database that an application can
process. It may contain parts of one or more tables.
Views are sometimes called virtual tables. To the application or the user, views
behave the same as tables. Views, however, have no independent existence.
Views allow you to look at data, but views are not part of the data.