Failed to save modifications to the server. Error returned: 'OLE DB or ODBC error: [DataSource.Error

Hi konradjonsson 

It seems both of the queries you want to append are from the same table in the same database. And I think your queries are good and I don't see any error.

Where do you use the Power Query Editor? In Power BI Desktop, Excel or Dataflow? If you are using Power BI Desktop, can you update it to the latest version and try the append operation again?

If updating the version of the application doesn't solve this problem, you could consider removing the applied steps one by one from the last step to check whether some specific transformation step caused this error. 

You could also first connect to the same table in both queries and append the queries before any transformation to check whether they can be appended. If there is no error, then add the proceeding steps to transform the queries. If you find a step would cause this error, remove it and think about adding it in the appended query.

Hope this helps.

Regards,
Community Support Team _ Jing
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