• Many times, a database table has more information than
we want to display. Or, perhaps a table does not have all the information we want
to display. For instance, in Example 8-1, seeing the Title and ISBN of a book
is not real informative - we would also like to see the Author, but that information
is not provided by the Titles table. In these cases, we can build our own virtual
table, displaying only the information we want the user to see.
• We need to form a different SQL statement in the RecordSource
property. Again, we won’t be learning SQL here. We will just give you the
proper statement.
Quick Example: Forming a Virtual Table
1. We’ll use the results of Example 8-1 to add the Author
name to the form. Replace the RecordSource property of the dtaTitles control with
the following SQL statement:
SELECT Author,Titles.ISBN,Title FROM Authors,[Title
Author],Titles WHERE Authors.Au_ID=[Title Author].Au_ID AND Titles.ISBN=[Title
Author].ISBN ORDER BY Author
This must be typed as a single line in the Command Text (SQL)
area that appears when you click the ellipsis by the RecordSource property. Make
sure it is typed in exactly as shown. Make sure there are spaces after ‘SELECT’,
after ‘Author,Titles.ISBN,Title’, after ‘FROM’, after
‘Authors,[Title Author],Titles’, after ‘WHERE’, after
‘Authors.Au_ID=[Title Author].Au_ID’, after ‘AND’, after
‘Titles.ISBN=[Title Author].ISBN’, and separating the final three
words ‘ORDER BY Author’. The program will tell you if you have a syntax
error in the SQL statement, but will give you little or no help in telling you
what’s wrong.
Here’s what this statement does: It selects the Author,
Titles.ISBN, and Title fields from the Authors, Title Author, and Titles tables,
where the respective Au_ID and ISBN fields match. It then orders the resulting
virtual table, using authors as an index.
2. Add a label box and text box to the form, for displaying
the author name. Set the control properties.
Label3:
Caption - Author
Text1:
DataSource - dtaTitles (select, don’t type)
DataField - Author (select, don’t type)
Locked - True
Name - txtAuthor
Text - [Blank]
When done, the form should resemble this:
3. Save, then rerun the application. The author’s names
will now appear with the book titles and ISBN values. Did you notice you still
haven’t written any code?
I know you had to type out that long SQL statement, but that’s
not code, technically speaking. Notice how the books are now ordered based on
an alphabetical listing of authors’ last names
