Q129077: How to Use the NODATA and NOREQUERY Clauses of USE

Article: Q129077
Product(s): Microsoft FoxPro
Version(s): WINDOWS:3.0
Operating System(s): 
Keyword(s): kbcode
Last Modified: 12-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
=======

The NOQUERY and NODATA clauses of the USE command are used with local and remote
views. A view is an updatable set of records that is stored in a database. Once
a view is created, you can open it with the USE command. This article provides
an example that illustrates the use of the NODATA and NOQUERY clauses.

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

The NOQUERY and NODATA clauses allow you to open a query without [ downloading
the data. They can be useful when you have a large set of records, and you want
to verify the structure of the result set before you download the data. The
NOREQUERY clause is used in conjunction with the USE <view> AGAIN command.
It prevents FoxPro from re-querying the data if you open the view in another
work area. Use the REQUERY() function when you need to retrieve the data.

The following example illustrates how to use the NODATA and NOREQUERY clauses on
a local view. A parameterized view is created with the CREATE SQL VIEW command
and opened with a USE...NODATA command. No records are displayed. Then the same
view is opened in another work area with the USE.. AGAIN NOREQUERY command. Note
that it is not updated until the REQUERY() function is executed. To run this
example, copy and paste the following code into a program file, and then run
it.

     LOCAL nViews, cCity

     OPEN DATA SYS(2004) + 'samples\data\testdata'
     * Creates an array that holds the names of all the views in the database
     nViews = ADBOBJECTS(a_View, 'VIEW')
     IF nViews > 0
        IF ASCAN(a_View, 'COMPANY_VIEW') > 0
           DELETE VIEW Company_view
        ENDIF
     ENDIF

     cCity = 'London'
     CREATE SQL VIEW Company_view AS ;
        SELECT cust_id, company, city ;
        FROM customer ;
        WHERE city = ?cCity

     IF USED('Company_view')
        USE IN Company_view
     ENDIF

     * Open the view without downloading the data:
     SELECT 0
     USE Company_view NODATA
     BROWSE NOWAIT
     =MESSAGEBOX(IIF(RECCOUNT() = 0, 'No data yet.', 'Now we have data'))

     * Download the data:
     ?REQUERY()
     SHOW WINDOW Company_View REFRESH
     =MESSAGEBOX(IIF(RECCOUNT() = 0, 'No data yet.', 'Now we have data'))

     * Modify the value of the parameter:
     cCity="Paris"
     SELECT 0
     USE Company_view AGAIN NOREQUERY
     BROWSE NOWAIT
     =MESSAGEBOX("City is "+cCity+chr(13)+"Query is not updated")
     ?REQUERY()
     =MESSAGEBOX("City is "+cCity+chr(13)+"Query is updated")

REFERENCES
==========

Visual FoxPro for Windows "Developer's Guide," version 3.0, Chapter 8, "Creating
Multi-Table Views."

Additional query words: VFoxWin

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

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