Just to double check, do we underline all keys or primary keys only?

raywu64 wrote:

Hopefully I'm not wrong, but my understanding is that on the ER diagram you underline keys. Keys meaning any unique attribute (relative to the entity set). 

 

In a database schema design, you only underline the primary key(s). 

 

If your table is in BCNF, generally the keys underlined will be the same in both cases anyways. 

Well, that's not quite right. We only underline the primary key in both ER diagram and relational schema.