Data truncated to 255 characters with Excel ODBC driver

When you retrieve external data using the Microsoft Excel 97 ODBC driver, fields that have more than 255 characters may be truncated to 255 characters.

Your data may be truncated to 255 characters if the first 8 records for the field(s) being truncated contain 255 or fewer characters. The Microsoft Excel ODBC driver will, by default, scan the first 8 rows of your data to determine the type of data in each column.

Even though you can change the Rows To Scan value in the ODBC Microsoft Excel Setup dialog box to something higher than 8 (but not higher than 16) this value is not being used by Excel. The Excel ODBC driver uses the TypeGuessRows DWORD value of one of the following registry key to determine how many rows to scan in your data:

• Excel 97
  HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Jet\3.5\Engines\Excel
• Excel 2000 and later versions
  HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Jet\4.0\Engines\Excel

To change the number of rows that the Excel ODBC driver scans to determine what type of data you have in your table, change the setting of the TypeGuessRows DWORD value.

NOTE: The following steps will only work if your source Excel file is saved in the Microsoft Excel Workbook file format. If it is saved in the Microsoft Excel 97 & 5.0/95 Workbook file format, the data will always be truncated to 255 characters.

Important This section, method, or task contains steps that tell you how to modify the registry. However, serious problems might occur if you modify the registry incorrectly. Therefore, make sure that you follow these steps carefully. For added protection, back up the registry before you modify it. Then, you can restore the registry if a problem occurs. For more information about how to back up and restore the registry, click the following article number to view the article in the Microsoft Knowledge Base:

For information about how to edit the registry, view the "Changing Keys And Values" Help topic in Registry Editor (Regedit.exe) or the "Add and Delete Information in the Registry" and "Edit Registry Data" Help topics in Regedt32.exe. Note that you should back up the registry before you edit it. If you are running Windows NT, you should also update your Emergency Repair Disk (ERD).

To change the setting for the TypeGuessRows value, follow these steps:

1. Close any programs that are running.
2. On the Start menu, click Run. Type regedit and click OK.
3. In the Registry Editor, expand the following key depending on the version of Excel that you are running:
   • Excel 97
     HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Jet\3.5\Engines\Excel
   • Excel 2000 and later versions
     HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Jet\4.0\Engines\Excel
4. Select TypeGuessRows and on the Edit menu click Modify.
5. In the Edit DWORD Value dialog box, click Decimal under Base. Type a value between 0 and 16, inclusive, for Value data. Click OK and quit the Registry Editor.

NOTE: For performance reasons, setting the TypeGuessRows value to zero (0) is not recommended if your Excel table is very large. When this value is set to zero, Microsoft Excel will scan all records in your table to determine the type of data in each column.

Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.