practise test.. Does This Look Right?

From: MadG <patrick4133_at_hotmail.com>
Date: Tue, 13 Mar 2001 23:15:56 GMT
Message-ID: <MSxr6.30402$p66.9874881_at_news3.rdc1.on.home.com>

I'm still a bit stuck, and I'm sorry if my question seems lame for this newsgroup. If my question is unwelcome please tell me, and I'll stop.

I didn't make an entity for the subject area because I thought that this would work out better.

However, I am not at all sure about the Supplement entity. I don't like the feel of it and don't
know what other options I have.
The supplement is not required, and there may be many to each ISBN.

The ERD would be:

TEXTBOOK(1) contains SUPPLEMENT(M)
TEXTBOOK(1) is affiliated to AFFILIATE(1)
TEXTBOOK(1) gets EVALUATE(1)
EVALUATE(M) is worth WEIGHT(1)

AFFILIATE(1) is published by PUBLISHER(M) {I need better verbs..}

MY PROGRESS IN NORMALIZATION ( is it 3nf yet? )

---

TEXTBOOK ( ISBN[PK], BOOKNAME, AUTHOR, AFF_NUM[FK TO AFFILIATE], YEAR, COST ) PUBLISHER ( PUB_NUM[PK], PUB_NUM, CONTACT, WEBSITE, LAST_CONTACT ) AFFILIATE ( AFF_NUM[PK], PUB_NUM[FK TO PUBLISHER], AFF_NAME ) SUPPLEMENT ( ISBN[ISBN FK TO TEXTBOOK], SUPPLEMENT [COMPOSITE PK] ) EVALUATE ( ISBN, BOOKNAME, SUBJECT[FK TO WEIGHT], CONTENT, EASE_READ, EXERCISES, COST )
BOOKNAME WOULD HAVE BEEN A CANDIDATE KEY, HOWEVER THE CHANCE OF INPUT ERROR IS TOO GREAT. WEIGHT ( SUBJECT, CONTENT_W, EASE_READ_W, EXERCISES_W, COST_W )

##################
###################

forwarded

> ---- Entites
> TEXTBOOK (ISBN[PRIMARY KEY], BOOKNAME, AUTHOR, AFF_NUM[FORIEGN KEY
> --A.TABLE], YEAR. COST (SUPPLEMENT)[REPEATING GROUP])
>
> PUBLISHER (PUB_NUM[PRIMARY KEY], PUB_NAME, CONTACT, WEBSITE, LAST_CONTACT)
>
> AFFILIATE (AFF_NUM[PRIMARY KEY], PUB_NUM[FOREIGN KEY -P.TABLE], AFF_NAME)
>
> ----
>
> Keep track of textbook features to be evaluated (content coverage,
> ease of reading, exercises, cost), the weights (1-3) associated with
> each of these features and the evaluation number (1-10) scored for
> each feature of a particular textbook.

Think of the entity 'Evaluation'.

Important questions: What attributes belong to an Evaluation? What identifies an Evaluation? Is the relationship between Evaluation and Textbook a one-to-one, one-to-many, many-to-one, or a many-to-many relationship?

> There is a requirement to identify the textbooks being evaluated for
> different subject areas (example: systems analysis and design;
> database systems; C++ programming)

Think of the entity 'Subject area' and ask the same questions. What attributes are there? How is a subject area identified. What type of relationship does it have with Book?

> I don not know how to take care of the repeating group. I had
> thought that perhaps I should create an entity SUPPLEMENT but from
> there I get stuck as to what to include.

You have to include of course the information in the repeating group itself, but also something that relates these records to the original records that they belonged to. What foreign key could do that?

Good luck,

--
  Jan Hidders

Received on Wed Mar 14 2001 - 00:15:56 CET