السلام عليكم .. احنا المس في نفس الواجب معطيتنا في السؤال الرابع غير الي هو :
Q.4 Consider the Library database.
Author ( authorname, citizenship, birthyear)
Book(isbn, title, authorname)
Topic(isbn, subject)
Branch(libname, city)
Instock(isbn, libname, quantity)
Give an expression in the relational algebra for each of the following queries:
a. Give all authors’ names born after 1940.
b. Give the title of each book on the topic of either alcohol or drugs.
c. Give the title and author of each book of which at least two copies are held in a branch located in Melbourne.
إذا ما عليكم أمر و تعرفون الحل تحطونه هنا 
IT244 Assignment 1 solution
العرض العادي
