Sink Mapping in Dataflow

Question

Why am I getting the error "The result has 0 output columns. Please ensure at least one column is mapped" when previewing data in a Dataflow sink, even though the mapping seems correct?

Answer 1

Hi @DataCoder
Thank you for your question and using the Microsoft Q&A platform.

This error typically occurs in Azure Data Factory (ADF) when there is a mismatch or misconfiguration in your Dataflow's sink settings or schema. Could you please check if the 'Allow schema drift' checkbox is ticked in your Azure Synapse Analytics Data Flow? If it is not ticked, please make sure to tick it.

Here are some common causes and steps to troubleshoot the issue:

1. Column Mapping:
   • Ensure Columns are Mapped Correctly: Double-check that each source column is mapped to a corresponding sink column in the Dataflow.
   • Refresh Schema: Sometimes, the schema might not have been updated correctly. Try refreshing the schema in both the source and sink.
2. Schema Mismatch:
   • Column Names and Data Types: Ensure that the column names and data types in your source match those in the sink. Any discrepancies can cause the mapping to fail.
   • Case Sensitivity: Be mindful of case sensitivity in column names. Some systems are case-sensitive, and a mismatch can lead to this error.
3. Sink Configuration:
   • Output Columns: Verify that the sink configuration is set up to accept the expected output columns.
   • Schema Drift: If using schema drift, ensure that the settings are correctly configured to handle dynamic columns.
4. Debug Mode:
   • Preview Data: Use the debug mode to preview data at different stages of your Dataflow to identify where the columns might be dropped.
   • Inspect Output: Preview the output of each transformation to see if the columns are still present.
5. Integration Runtime:
   • Correct IR: Ensure you are using the correct Integration Runtime (IR) for the Dataflow, as mismatched IR settings can sometimes cause schema issues.

Here are some steps to follow to troubleshoot:

1. Check Column Mapping in Sink:
   • Go to the sink in your Dataflow.
   • Check the "Mapping" tab to ensure all required columns from the source are mapped to the sink.
2. Preview Data at Each Step:
   • Use the data preview feature at each step of the Dataflow to verify the columns and data.
   • This will help identify at which point the columns are being dropped.
3. Refresh and Validate Schemas:
   • Refresh the schema in the source and sink settings.
   • Validate that the columns are correctly recognized and mapped.

Hope this helps. Do let us know if you any further queries.

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