About the Series …
This article continues the series, MS Access for the
Business Environment. The primary focus of this series is an
examination of business uses for the MS Access relational database management
system. The series is designed to provide guidance in the practical application
of data and database concepts to meet specific needs in the business world. The
majority of the procedures I demonstrate in this article and going forward will
be undertaken with MS Access 2003, although most of the concepts that we
explore in the series will apply to earlier versions of MS Access, as well.
For more information on the series, as well as the hardware
/ software requirements to prepare for the tutorials we will undertake, please
see Tutorial 1: Create
a Calculated Field with the Expression Builder.
Introduction to this
Tutorial
In our
last lesson, Access
Query Techniques: Subqueries, Part I, we
introduced subqueries within the context of MS Access, and practiced their
creation and use in rendering a result dataset to meet illustrative business
needs. As a part of our exploration of subqueries, we examined the syntax
surrounding the use of a straightforward sample subquery; we then began an
illustrative, hands-on example of the use of a subquery in a multi-step
practice exercise. After evolving an initial query, we created a second query,
within which we nested the first, to demonstrate the operation of a subquery in
our practice exercise. Finally, we briefly discussed various aspects of the
results datasets that we obtained in each step of the practice examples.
Before moving to our next
article, Access Query Techniques: Subqueries,
Part II, we will
first consider a keyword whose use we will see again in the second half of our
exploration of subqueries, as well as elsewhere. We will overview the TOP
keyword, and get a feel for its operation in an undistracted scenario, before
proceeding into the creation of a subquery that leverages the keyword to
illustrate more sophistication in the use of subqueries than we saw in Part
I.
The objective of this lesson is
to introduce the TOP keyword as it is used in Microsoft Jet SQL, and to
explore ways we can use it to meet illustrative business needs. To accomplish
this, we will follow our approach in previous lessons, and perform the
following activities surrounding our examination of the TOP keyword:
- an examination of the syntax surrounding the use of TOP;
-
an illustrative, hands-on example of the use of TOP in a practice
exercise; -
a similar example where we use the optional PERCENT
keyword, in conjunction with TOP, to return a percentage, versus a
number, of rows in an illustrative dataset; -
a brief discussion of the results datasets that we obtain in each
of the practice examples.
We will use the Northwind sample database that
installs with MS Access for purposes of this lesson, in an attempt to make our
discussion useful to virtually anyone who has access to the application.
