Where is Zipcode located in the Zipcode table

I have an elementary question
In the Qodly documentation,
About images in data model objecs in the Programming guide
Where is Zipcode located in the Zipcode table

As explained under the image, “Zipcodes are used as primary keys of the ZipCode table”, thus the zipcode is the ZipCode.ID attribute. However it is not clearly stated that ID is the primary key for ZipCode table.
In the getCityName function below, the zip=ds.ZipCode.get(zipcode) statement gets the zip entity by passing the primary key (zipcode) as parameter.

Thank you for your response

I was aware that the ID value was managed automatically by qodly
Since Zipcode is based on the user’s specifications, I need to create an attribue separately from the ID.
I was aware of it
And we thought it would be appropriate to assign a newly created ZipCode to the Primary Key

Referring to this image, qodly does not allow primary keys other than IDs

Is it different from 4D?

Qodly allows you to declare any longint or string attribute as primary key for a dataclass. The primary key can be filled automatically or not. It is not different from 4D.

Thank you

I was looking for it in Canvas
I’ve discovered that changing the Primary key is done with property, not canvas

But the question remains

Why did the user assign the zipcode of the purpose of use to the ID that Qodly automatically manages?

The question is, are there any other purposes for Qodly?

I suppose it is only a design choice for this example. Imagine zipcodes are imported from a file and you know they are all unique. When creating entities at import, assigning zipcodes to IDs makes sense. It could be handled differently in other designs. Note that Qodly can manage ID automatically, but it is not mandatory.

Thank you

The ID is an atribute that is automatically created when you create a new data class in Qodly.
At the same time, it is set as the primary key.

Does it mean that the subsequent use of the ID can be managed in the same way as the attribute created by the user