After searching online, there is a simple introduction as follows, which also shows that the E-R diagram mentioned in Introduction to Database System is relative to the conceptual model and is strictly defined in the database. It is an entity relationship method proposed by Chen in 1976. This method uses E-.

E-R diagram provides a method to express entity types, attributes and relationships.

▲ Real body shape: represented by rectangle.

▲ Attribute: represented by an ellipse.

▲ Contact: represented by a diamond.

< Introduction to Database System > Third Edition, find a book to read. I believe in your ability. In addition, Baidu Encyclopedia also has a more detailed introduction. The link is as follows: /view/ 15236.htm and the following ppt explain the drawing of ER diagram/view/21bb077e27284b73f2425090.html Here is a concrete example/view/7f5761e8998fc22bcd6544. D8c9782af789eb172dc8cf.html feels like a means of modeling with graphics. There is no great demand for books. The information on the internet is already very detailed. Please continue to communicate if you have any questions.