# \#polybase
**URL:** https://community.cdata.com/tag/polybase/229.md
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## [ODBC drivers in Polybase - Issue creating an external table with mismatched metadata](https://community.cdata.com/t/odbc-drivers-in-polybase-issue-creating-an-external-table-with-mismatched-metadata/381)
**Author:** [@LaurenH](https://community.cdata.com/u/LaurenH)\
**Replies:** 0\
**Last updated:** [September 6, 2023, 9:05pm UTC](https://community.cdata.com/t/odbc-drivers-in-polybase-issue-creating-an-external-table-with-mismatched-metadata/381 "2023-09-06T21:05:40Z")
An error will be thrown when the column metadata defined in the CREATE EXTERNAL TABLE statement does not match the driver’s reported column metadata in the source table. The error will detail which columns are mismatched…
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## [ODBC drivers in Polybase: File path permissions should match the user accessing them with the identity of the SQL Server process](https://community.cdata.com/t/odbc-drivers-in-polybase-file-path-permissions-should-match-the-user-accessing-them-with-the-identity-of-the-sql-server-process/335)
**Author:** [@LaurenH](https://community.cdata.com/u/LaurenH)\
**Replies:** 0\
**Last updated:** [August 16, 2023, 6:12pm UTC](https://community.cdata.com/t/odbc-drivers-in-polybase-file-path-permissions-should-match-the-user-accessing-them-with-the-identity-of-the-sql-server-process/335 "2023-08-16T18:12:08Z")
When accessing CSV, Excel, etc files using Polybase, those drivers are typically configured with file paths, note that the identity of the user accessing those files with be the identity of the SQL Server process so make…
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## [ODBC drivers in Polybase: Changes with connection settings and metadata are not reflected](https://community.cdata.com/t/odbc-drivers-in-polybase-changes-with-connection-settings-and-metadata-are-not-reflected/334)
**Author:** [@LaurenH](https://community.cdata.com/u/LaurenH)\
**Replies:** 0\
**Last updated:** [August 16, 2023, 5:35pm UTC](https://community.cdata.com/t/odbc-drivers-in-polybase-changes-with-connection-settings-and-metadata-are-not-reflected/334 "2023-08-16T17:35:34Z")
Issue: Sometimes, changes to a DSN meant to change driver behavior, how metadata is exposed, or what metadata exists will not be immediately apparent when the driver is used from Polybase. In those cases, Polybase likely…
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## [ODBC drivers in Polybase: Object reference error occurring when creating external table](https://community.cdata.com/t/odbc-drivers-in-polybase-object-reference-error-occurring-when-creating-external-table/331)
**Author:** [@LaurenH](https://community.cdata.com/u/LaurenH)\
**Replies:** 0\
**Last updated:** [August 14, 2023, 8:51pm UTC](https://community.cdata.com/t/odbc-drivers-in-polybase-object-reference-error-occurring-when-creating-external-table/331 "2023-08-14T20:51:06Z")
Error: “Object reference not set to an instance of an object.” Cause will depend on situation, check driver any polybase logs. Some possible causes include: A User DSN was specified within the CONNECTION\_OPTIONS of t…
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## [ODBC drivers in Polybase: Object reference error occurring when creating external table](https://community.cdata.com/t/odbc-drivers-in-polybase-object-reference-error-occurring-when-creating-external-table/330)
**Author:** [@LaurenH](https://community.cdata.com/u/LaurenH)\
**Replies:** 0\
**Last updated:** [August 14, 2023, 6:51pm UTC](https://community.cdata.com/t/odbc-drivers-in-polybase-object-reference-error-occurring-when-creating-external-table/330 "2023-08-14T18:51:27Z")
Error: “Object reference not set to an instance of an object.” Cause will depend on situation, check driver any polybase logs. Some possible causes include: A User DSN was specified within the CONNECTION\_OPTIONS of t…
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## [ODBC drivers in Polybase: Avoiding issues with NVARCHAR columns](https://community.cdata.com/t/odbc-drivers-in-polybase-avoiding-issues-with-nvarchar-columns/329)
**Author:** [@LaurenH](https://community.cdata.com/u/LaurenH)\
**Replies:** 0\
**Last updated:** [August 14, 2023, 6:13pm UTC](https://community.cdata.com/t/odbc-drivers-in-polybase-avoiding-issues-with-nvarchar-columns/329 "2023-08-14T18:13:52Z")
Polybase has a maximum row size of 32 KB in SQL Server (or 1 MB in Azure Synapse Analytics). As a good rule of thumb, when creating NVARCHAR columns with the CREATE EXTERNAL TABLE statement, set the size to 255 unless yo…