Tableau prep not deleting duplicate records in SQL Server on-premise database

Question

We are working on data cleaning project. We are attempting POC on Tableau using Northwind database on SQL Server 2019.

We have a Category table with ID (primary), Name, description, picture. We intend to clean duplicate data if same category name is given, irrespective of other columns.

Being small sample data user can see all records but Tableau prep builder shows redundant categories added by us. We use "exclude" in flow. And for output we run the flow.

Steps taken on UI after successful connection:

1. Add Data: Category
2. View and Clean data: Selected Id of duplicate records and clicked on exclude
3. Add Output: Save output to : Same server, same database, same table (category)
4. Run Flow

I get an error:

Unable to run the flow. Check the error notification for more details

Alert at top right shows

System error: AqlProcessor evaluation failed: [Microsoft][ODBC Driver 17 for SQL Server][SQL Server]Cannot insert explicit value for identity column in table 'Categories' when IDENTITY_INSERT is set to OFF.

Is tableau attempting to delete whole data and insert?

I am absolutely beginner of Tableau