Q136940: Valid Uses for the View Parameters

Article: Q136940
Product(s): Microsoft FoxPro
Version(s): WINDOWS:3.0
Operating System(s): 
Keyword(s): 
Last Modified: 15-FEB-2000

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The information in this article applies to:

- Microsoft Visual FoxPro for Windows, version 3.0 
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SUMMARY
=======

This article explains how to use the "?" character to build a parameterized
view. In particular, it addresses the issue of the location of the "?" in the
WHERE clause, and of using macro substitution with parameterized views.

MORE INFORMATION
================

View parameters provide a mechanism for value substitution, not macro
substitution.

In the View Designer, you can specify parameters on the right side of the WHERE
clause (and the HAVING clause). However, parameters are still legal on the left
side of the WHERE clause.

Both of the following commands create a valid parameterized SQL view:

     CREATE SQL VIEW viewname AS SELECT * FROM tablename;
        WHERE field1 = ?param1

-or-

     CREATE SQL VIEW viewname AS SELECT * FROM tablename;
        WHERE ?param1 = view1

In both cases, when the VIEWNAME view is opened, the user is prompted for a value
for PARAM1, which is then used in the WHERE clause.

An example of macro substitution in the left side of the clause would be if the
following view allowed the user to supply a field name for FIELDPARAM rather
than just a value.

     CREATE SQL VIEW viewname AS SELECT * FROM tablename;
        WHERE ?fieldparam = ?param1

Although this is a valid view, the effect is to compare the value entered for
?FIELDPARAM with that entered for PARAM1 for all records. The macro substitution
does not occur.

Additional query words: VFoxWin question mark parameterized view database

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Keywords          :  
Technology        : kbVFPsearch kbAudDeveloper kbVFP300
Version           : WINDOWS:3.0

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