Microsoft KB Archive/191522

= FIX: TABLEUPDATE Fails in Remote View With Empty Memo Field =

Article ID: 191522

Article Last Modified on 3/2/2005

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APPLIES TO


 * Microsoft Open Database Connectivity Driver for Visual FoxPro 3.0
 * Microsoft Open Database Connectivity Driver for Visual FoxPro 5.0
 * Microsoft Data Access Components 2.5

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This article was previously published under Q191522



SYMPTOMS
You have a remote view to a Visual FoxPro table using the Visual FoxPro ODBC driver. When you attempt to issue a TABLEUPDATE after replacing a memo field value with an empty string (""), the TABLEUPDATE fails with the following error:

Connectivity error: [Microsoft][ODBC Visual FoxPro Driver]Invalid string or buffer length.

NOTE: This may also happen connecting through the Visual FoxPro ODBC driver from other clients such as MSQuery.



RESOLUTION
As a workaround, you can set the field to accept NULL values and replace the field value with NULL rather than "".



STATUS
Microsoft has confirmed this to be a bug in the Microsoft products listed at the beginning of this article. This bug has been corrected in Visual FoxPro 6.0.



Steps to Reproduce Behavior
  Run the following code from a program (.PRG) file. It programmatically creates an ODBC User DSN called "VFP TestDB" to connect to a database container called TestDB.dbc. The .dbc is created, a table called TESTTAB is created, and a remote view (called TESTTAB_REMOTE) to that table is created. The view is USEd, the Notes memo field is replaced with the value "", and the TABLEUPDATE is issued. TABLEUPDATE returns .F. and the error generated is:

Connectivity error: [Microsoft][ODBC Visual FoxPro Driver]Invalid string or buffer length.

LOCAL lcDir, lcSettings, laErrorArray[1] CLEAR SET EXCLUSIVE OFF CLOSE DATABASE ALL

* Declare API function to create ODBC User DSN. DECLARE INTEGER SQLConfigDataSource IN odbccp32.DLL ; INTEGER, INTEGER, STRING, STRING lcDir = SET('DEFAULT')+CURDIR lcSettings="DSN=VFP TestDB"+CHR(0)+; "Description=VFP TestDB"+CHR(0)+; "SourceDB="+lcDir+"testdb.dbc"+CHR(0)+; "SourceType=DBC"

* Call API function to create ODBC User DSN. =SQLConfigDataSource(0,1,"Microsoft Visual FoxPro Driver",lcSettings)

SET SAFETY OFF * Make the database. CREATE DATABASE 'TESTDB.DBC'

* Make the table and index. CREATE TABLE 'TESTTAB.DBF' NAME 'TESTTAB' (PK C(5) NOT NULL, ;        NOTES M NOT NULL)

ALTER TABLE 'TESTTAB' ADD PRIMARY KEY PK TAG PK

CLOSE DATABASE ALL OPEN DATABASE testdb SHARED

* Make the remote view. CREATE SQL VIEW "TESTTAB_REMOTE" ; REMOTE CONNECT "VFP TestDB" ; AS SELECT * FROM TESTTAB Testtab

* Set the view properties. DBSETPROP('TESTTAB_REMOTE', 'View', 'UpdateType', 1) DBSETPROP('TESTTAB_REMOTE', 'View', 'WhereType', 1) DBSETPROP('TESTTAB_REMOTE', 'View', 'FetchMemo', .T.) DBSETPROP('TESTTAB_REMOTE', 'View', 'SendUpdates', .T.) DBSETPROP('TESTTAB_REMOTE', 'View', 'UseMemoSize', 255) DBSETPROP('TESTTAB_REMOTE', 'View', 'FetchSize', 100) DBSETPROP('TESTTAB_REMOTE', 'View', 'MaxRecords', -1) DBSETPROP('TESTTAB_REMOTE', 'View', 'Tables', 'TESTTAB') DBSETPROP('TESTTAB_REMOTE', 'View', 'Prepared', .F.) DBSETPROP('TESTTAB_REMOTE', 'View', 'CompareMemo', .T.) DBSETPROP('TESTTAB_REMOTE', 'View', 'FetchAsNeeded', .F.) DBSETPROP('TESTTAB_REMOTE', 'View', 'FetchSize', 100) DBSETPROP('TESTTAB_REMOTE', 'View', 'Comment', "") DBSETPROP('TESTTAB_REMOTE', 'View', 'BatchUpdateCount', 1) DBSETPROP('TESTTAB_REMOTE', 'View', 'ShareConnection', .F.) * Set the view field properties. DBSETPROP('TESTTAB_REMOTE.pk', 'Field', 'KeyField', .T.) DBSETPROP('TESTTAB_REMOTE.pk', 'Field', 'Updatable', .T.) DBSETPROP('TESTTAB_REMOTE.pk', 'Field', 'UpdateName', 'TESTTAB.pk') DBSETPROP('TESTTAB_REMOTE.pk', 'Field', 'DataType', "C(5)") DBSETPROP('TESTTAB_REMOTE.notes', 'Field', 'KeyField', .F.) DBSETPROP('TESTTAB_REMOTE.notes', 'Field', 'Updatable', .T.) DBSETPROP('TESTTAB_REMOTE.notes', 'Field', 'UpdateName', ;        'TESTTAB.notes') DBSETPROP('TESTTAB_REMOTE.notes', 'Field', 'DataType', "M")

SET SAFETY ON

* Add a couple of records to the table. INSERT INTO TESTTAB VALUES ("A", "1234567890") INSERT INTO TESTTAB VALUES ("B", "1234567890") CLOSE DATABASE ALL OPEN DATABASE testdb

* Open the view. USE testdb!TESTTAB_remote

*Replace field with "" and issue TABLEUPDATE REPLACE NOTES WITH "" IF !TABLEUPDATE(.T.) ?"Tableupdate failed with the following error:" =AERROR(laErrorArray) ?laErrorArray(2) =TABLEREVERT ENDIF 

TABLEUPDATE returns .F. indicating that it failed. The error returned from AERROR is:

Connectivity error: [Microsoft][ODBC Visual FoxPro Driver]Invalid string or buffer length.

If the memo field is set to accept nulls and the REPLACE replaces the value with NULL, the error does not occur. You can do the following within Visual FoxPro:

You can demonstrate this by changing the preceding CREATE TABLE line to read:

CREATE TABLE 'TESTTAB.DBF' NAME 'TESTTAB' (PK C(5) NOT NULL, ;     NOTES M NULL)

-and- change the REPLACE line to read:

REPLACE NOTES WITH NULL

To employ this workaround from within a Visual FoxPro form, for instance, make the following changes:

  Set the following environment setting in Visual FoxPro 5.0. This makes the NULL display as an empty string. SET NULLDISPLAY TO ""   In an Editbox Valid method, you could add the following code to ensure that the NULL is used if the Value property of the Editbox is empty: IF EMPTY(This.Value) This.Value = NULL ENDIF 

