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Chapter 10: Problem 12

What does the term unnormalized relation refer to? How did the normal forms develop historically from first normal form up to Boyce-Codd normal form?

Short Answer

Expert verified
Unnormalized relation is essentially a database table with redundancy and potential inconsistencies. Database normalization emerged to combat these issues, and started from First Normal Form (1NF) which emphasized atomicity and a primary key for each table. Then came Second Normal Form (2NF) to handle partial dependency issues, followed by Third Normal Form (3NF) addressing transitive dependencies. Finally, Boyce-Codd Normal Form (BCNF) was introduced to handle anomalies not resolved by 3NF, primarily in databases with multiple overlapping candidate keys.

Step by step solution

01

Defining Unnormalized Relation

The term 'unnormalized relation' refers to a database table that contains redundant data, or data that can be derived from other data in the same table. This can often lead to inconsistencies and inaccuracies in a database.
02

Understanding First Normal Form (1NF)

First Normal Form (1NF) was introduced to handle the issues of unnormalized relations. It requires that each column in a table should contain atomic (indivisible) values, and there should be a primary key to uniquely identify each row.
03

Leading to Second Normal Form (2NF)

The Second Normal Form (2NF) emerged to address the issue of partial dependencies, i.e., a situation where a non-key attribute is dependent on only a part of the primary key. In 2NF, all non-key attributes must be fully dependent on the primary key.
04

Transition to Third Normal Form (3NF)

The third normal form (3NF) was developed to rectify the issues of transitive dependencies, where a non-key attribute is dependent on another non-key attribute. In 3NF, every non-key attribute should be directly dependent on the primary key.
05

Introduction of Boyce-Codd Normal Form (BCNF)

The Boyce-Codd Normal Form (BCNF) was introduced to handle certain anomalies not dealt by 3NF, especially in complex databases with multiple overlapping candidate keys. In BCNF, for every non-trivial functional dependency X -> Y, X must be a super key.

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Most popular questions from this chapter

What is a functional dependency? What are the possible sources of the information that defines the functional dependencies that hold among the attributes of a relation schema?

What role do Armstrong's inference rules- -the three inference rules IR 1 through IR3-play in the development of the theory of relational design?

Discuss attribute semantics as an informal measure of goodness for a relation schema.

, Odate, Cust#, Total_amount) ORDER- ITEM(O#, I#, Qty_order… # Consider the following relations for an order-processing application database at \(\mathrm{ABC},\) Inc. ORDER (O#, Odate, Cust#, Total_amount) ORDER-ITEM(O#, I#, Qty_ordered, Total_price, Discount\%) Assume that each item has a different discount. The Total_PRICE refers to one item, OOATE is the date on which the order was placed, and the Total_AMOUNT is the amount of the order. If we apply a natural join on the relations ORDER-ITEM and ORDER in this database, what does the resulting relation schema look like? What will be its key? Show the FDs in this resulting relation. Is it in \(2 \mathrm{NF}\) ? Is it in \(3 \mathrm{NF}\) ? Why or why not? (State assumptions, if you make any.)

Discuss insertion, deletion, and modification anomalies. Why are they considered bad? Illustrate with examples.
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