Engineering adds columns for relation

Question

I'm absolutely can't understand logic of the forward engineering process.
Why it adds ADDITIONAL PK columns into my tables with relation?
For example, two tables: CLASS (class_id, name) and TYPE(type_id, name, class_id) with 1-N relation (class.class_id - type.class_id).
After engineering logical model into relational, in a last one I can see new columns:
class.class_id1, type.class_class_id1
How to avoid it? I want to use my own columns for relation!  

Answer 1

Hi,
you don't have a primary key for entity CLASS in logical model - that's fine. However in relational model you need a PK existing in CLASS table in order to have foreign key from table TYPE to table CLASS.
So new surrogate key column is created - default naming template is {table abbr}_ID and since you don't have table abbreviation it takes table name and creates column CLASS_ID and it becomes CLASS_ID1 because you already have a column CLASS_ID.
For table TYPE - foreign key column is created referring to column CLASS_ID1 - default naming template is {ref table}_{ref column} - this is how the name for the column is set to CLASS_CLASS_ID1.
If you don't want to create primary identifiers in logical model then you should not add PK and FK attributes in related entities - PK/FK columns will be created automatically during engineering to relational model - you need to set related templates.
Otherwise you can create PK identifier and related attributes added to it and FK attributes will be maintained automatically.
Philip