title: Azure SQL Database SYNC column does not allow nulls warning
body: <p>I have a Microsoft SQL Data Sync Agent job set up to sync our local server to Azure. It was working great, then we made a few updates locally and it didn't remove the deleted rows from Azure, and now the sync fails with a warning:</p>
  
  <pre><code>Sync completed with warnings in 708.02 seconds. 
  Upload:   4646 changes applied/155 failed   
  Download: 680 changes applied/0 failedData Sync will stop synchronizing changes for this sync group member in -60 days if the failures are not resolved.    
  Upload - errors for first 5 rows that failed to apply:Error #1: SqlException Error Code: -2146232060 - 
  SqlError Number:515, Message: Cannot insert the value NULL into column 'ModelID', table 'dbo.ModelYears'; column does not allow nulls. INSERT fails. 
  SqlError Number:3621, Message: The statement has been terminated. Error #2: SqlException Error Code: -2146232060 - 
  SqlError Number:515, Message: Cannot insert the value NULL into column 'ModelID', table 'dbo.ModelYears'; column does not allow nulls. INSERT fails. 
  SqlError Number:3621, Message: The statement has been terminated. Error #3: SqlException Error Code: -2146232060 - 
  SqlError Number:515, Message: Cannot insert the value NULL into column 'ModelID', table 'dbo.ModelYears'; column does not allow nulls. INSERT fails. 
  SqlError Number:3621, Message: The statement has been terminated. Error #4: SqlException Error Code: -2146232060 - 
  SqlError Number:515, Message: Cannot insert the value NULL into column 'ModelID', table 'dbo.ModelYears'; column does not allow nulls. INSERT fails. 
  SqlError Number:3621, Message: The statement has been terminated. Error #5: SqlException Error Code: -2146232060 - 
  SqlError Number:515, Message: Cannot insert the value NULL into column 'ModelID', table 'dbo.ModelYears'; column does not allow nulls. INSERT fails. 
  SqlError Number:3621, Message: The statement has been terminated.     
  For more information, provide tracing ID ‘92002a08-b374-4579-b58c-a5164e820767’ to customer support.
  </code></pre>
  
  <p>The ModelID column does not allow nulls on either table, so I'm not sure what is causing the error.</p>
  
  <p>I truncated ModelYears_dss_tracking and ModelYears on Azure as one forum suggested, and it did repopulate the tables, but it's still throwing the warnings.</p>