Question: 1. What isData-Manipulation Language (DML)? There are four types of access in DML, explain each one.
2. Assume we have a Library Database consists of the following relations:
author(author_id, first_name, last_name)
author_publication(author_id, publication_id, author_position)
book(book_id, book_title, month, year, editor)
publication(publication_id, title, book_id)
Note: (editor) in book's relation refers to (author_id) in author's relation. Some of authors are book editors.
(a) Underline the appropriate primary keys/foreign keys in the above relations.(mark: 1)
(b) Write two relational algebra expressions that retrieve:
- The last names of all authors who are book editors only.
- The first name of all authors who are not book editors.
3. (a) Consider that you are asked to design an entity relationship diagram based on the below scenario:
A university consists of a number of departments (id, d_name) and each department offers some courses. A number of modules make up each course. Students enroll their Id, full name, and gender in a particular course and take modules towards the completion of that course. Each module is taught by a lecturer from the appropriate department.
(b) We can convert any weak entity set to a strong entity set by simply adding appropriate attributes. Why, then do we have weak entity sets? Write about the weak entities for several reasons. (0.5 Mark)
4. Convert the following ER diagrams into relational schemas with the primary key defined for each relation.
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Attachment:- IT244Assignment1Questions.rar