我试图为一个简单的库数据库绘制一个ER图和SQL。
我有以下实体:
Book (holds the ISBN as key, book title, author)
Copy (copyID of a copy of a book, dateAcquired, dateDestroyed)
Member (MemberID, name, address)
Loaned (i guess the date due and the date back and obviously foreign keys for memberID and copyID)
成员还可以是学生或Staff。所以我认为这应