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I request the assistance I work on the library database, But I have problem on the erd and relationship between entity ,if any one can help me I am grateful to him .
this my project if any one can add some entity and the erd please:
The system contains entities that act and participate with the system , these entities are :

Employee Entity : each employee has an ID, Name, DOB , Address , telephone # , and supervised by other employee. The employee deal with supplier who supply the books, and treat each order comes from customer

Book Entity : each book has an ID , Name , Author Name , Book Category , and Price of the book.

Customer Entity : each customer has an ID, Name, Address , Telephone # , the customer is person who borrowing books from the library .

Supplier Entity : each supplier has an ID , Name , Telephone # , Address , the supplier is supply the library with different category of books.

Order Entity : each order has an ID , order date , delivery date , ID for the employee , and the ID for the customer who borrowed the books , Quantity of the order .

Edited by huss_584: n/a

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Last Post by huss_584
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well the first apparent error i see is the many to many relationship between the book and customer as one book can be loaned by many customer and a customer can loan many books, it is also not uncommon for a library to more than one copy of the same book, instead you should have a composite entity between customer and book entities and have a book_loan entity. also i hope you're not using the book's ISBN number as the primary that could be troublesome if you have more than one copy a book instead use a composite primary key (the ISBN and a surrogate key).

Edited by baki100: n/a

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ouch you use chen model i'll have a look at it and try and make out heads or tails from that doc

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