Is relational schema into the ER diagram, the some properties can be as physical properties, can also as a contact properties, such as a T1 (a1, a2, a3) one is the master key, 3 is a foreign key, can 2 as entity T1 attribute, and attribute can be as a link between 1 and 3?
T1 (a1, a2, a3), one is a primary key, and 3 are foreign keys, and a3=a1. This link itself with its own, needs to be converted to two entities? Can an entity T1, with two parallel lines to connect a diamond, it can be? Thank you very much!

CodePudding user response:

May be the wrong, depends on the specific topic