Bug 64377

I wouldn't prefer an automatically added and hidden primary-key-field. 
When you create a table without a primary-key a dialog in Base appears:
"No primary key ... you can only enter data with a primary key ... should the primary key created now?"
At this moment the user has only to press a button and will see the primary key in his table. He will be able to create relations between tables, because the primary-key isn't hidden and he could see the field-type of this key.
For many people the primary-key with autovalue and field-type "Integer" is the default. But there are also tables, which would work better without this automatic.
Example: 
table - "Gender"
fields - "ID", "Gender", "Title", "Salutation"
"ID" would be varchar with 1 char. Content of this field would be "m" and "f", while the content of "Gender" is "male" and "female".
I also use tables with only one row for settings of the database, where I change the value. Primary key in this tables has the field-type "Bool".

The only bug in this moment is: It isn't possible to add a primary key in an existing table without primary key while using the GUI. It is possible to create such a value using the direct SQL-mode. You have to decide the creating of a primary-key when creating the table. There is a warning, when you will save a table without creating such a key. If somebody ignores this warning it should be possible to change this with the GUI - and not hidden. But this is https://bugs.freedesktop.org/show_bug.cgi?id=61547

Please Note

(In reply to comment #1)
> I wouldn't prefer an automatically added and hidden primary-key-field.

The request is not asking to add hidden primary-key-field.
It is asking "add a hidden ROWID field",
which "act like a primary key field" at certain times. 
may be some thing similar to what Oracle have.

Only problem in Oracle is there is no guaranty that ROWID of a record stay constant for the life time of the record. It changes when we/system reorg a table.
 
> When you create a table without a primary-key a dialog in Base appears:
> "No primary key ... you can only enter data with a primary key ... should
> the primary key created now?"

Not much help for a new bee.
Basically most first time users dont understand the concept of primary key, foreign key, and relational integrity.  

> The only bug in this moment is: It isn't possible to add a primary key in an
> existing table without primary key while using the GUI. 

No, I dont think you need to force user to create a primary key all the time.
Oracle, MS-SQL, MS-Access dont do that.
Still corresponding GUI tools like SQL-Developer, TOAD, SQL-Server Management Studio, and also I think MS-Access allow user to edit the table content.

Adding self to CC if not already on