Database Principles Question.. ... Answer must not from wikis or other sources p

Question

Database Principles Question.. ... Answer must not from wikis or other sources pls..

I am not a fan of using Wikis for academic reference material, but easy to understand definition is just that...easy to understand. First normal form enforces these criteria: Eliminate repeating groups in individual tables. Create a separate table for each set of related data. Identify each set of related data with a primary key Put simply, a table is in 2NF if it is in 1NF and every non-prime attribute of the table is dependent on the whole of every candidate key. Use these definitions to explain the following two observations: A 1NF violations is usually the result of a M:N relationship that has not been simplified by an associative table. Associative tables are rarely in or beyond 2NF.

Explanation / Answer

Explanation of the above Question

Consider the following tables like as

STUDENT (STUDENT_NUMBER… ADVISOR_NUMBER, ADVISOR_NAME) containing different fields, here STUDENT_NUMBER are one of the fields, it is acting as Primary key for STUDENT table, it is 1st NF.

COURSE (COURSE_NUMBER…)

GRADE (STUDENT_NUMBER, COURSE_NUMBER…)

First of all 1st NF XXX (what u consider name of the table) table to three tables, Consider all in 2NF. That means each non-key Field depends on the entire primary key.

The above all three tables in 2NF

From the above tables   STUDENT is not in 3NF, because ADVISOR_NAME field depends up on ADVISOR_NUMBER field, it is not part of the STUDENT primary key.

To convert STUDENT to 3NF , you remove ADVISOR_NAME field from the STUDENT table place it into a table with ADVISOR_NUMBER as the Primary key.

So we can write as First Question Explanation from the above Condition like below one.

ADVISOR (ADVISOR_NUMBER, ADVISIOR_NAME)

From the above example you can observe as M:N relationship between the STUDENT and COURSE has been converted into two 1:M relationships.

That is one is between the STUDENT and GRADE, other is COURSE and GRADE.

           

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