Why I Always Fail To Manually Train A Model?

Dear all,

Why I always fail to manually train a model in Management Studio?

ZhaoHui Tang recommends me to untrain the model first. So I untrained it like this.

DELETE FROM Decision_Tree.CONTENT

Then I train it like this.

INSERT INTO Decision_Tree
(Age, Bike_buyer, Customer_Id, Gender)
OPENQUERY ([AdventureWorksDW], 'SELECT Age, Bike_buyer, Customer_Id, Gender FROM Training_table');

The error message is

Error (Data mining): The mining structure , Decision_Tree is already trained and does not
support incremental updates. Before using the INSERT INTO statement, use DELETE FROM <object>.

Why is that so? I already untrained the model. The model has been made and processed
outside Management Studio, i.e., in the Visual Studio.

Thank you,

Bernaridho