External Content Type from SQL View using inner joins

Hi,

I have a problem creating an external content type from a view in SQL.
This view joins about 8 tables together to give me the results I need. When I connect to the Database in SharePoint Designer to create my operations,
I see that some of the columns of the view are seen as a primary key value, although in the view in SQL they are not seen as a key (on a view you can't even set primary keys).  I also have a calculated column ID, which I want to be my primary key value.

When I want to add for example a "Read Item" operation, I am only able to map the identifiers that the SharePoint designer has found.
So it is not possible to use the ID column as identifier, cause he want to map this field on a column he sees as primary key.

I tried to do the same with another view, but for this ones no primary key columns were found and I was able to assign my own.
How can I solve this problem?

Thanks in advance.

Kr,

Mathieu