Chapter 6 Normalization

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Normal forms To eliminate redundancy and potential update related issues, we have identified several normal forms for relational schemas such that if a schema is in one of these forms, it has certain predictable properties. The first normal form(1NF) is equivalent to the definition of the relational data model saying that the value of an attribute must be atomic. The second normal form(2NF) sates that a schema must not have an FD X → Y such that X is a strict subset of the key of that schema. The third normal form(3NF) is thought to be ultimate one, but Boyce and Codd came up with the BCNF to cut away more redundancy. 24
What does that mean Every RDB is in 1NF. The rest is up in the air. For example, given the table Person(SSN, Name, Address, Hobby), it is not in 2NF, since it has an FD, SSN → Hobby, where SSN is part of its key: {SSN, Hobby}. On the other hand, once we split it into two tables, with SSN being the key, Person(SSN, Name, Address) with FD SSN → Name, Address, and Hobby(SSN, Hobby) with empty FD, then they both belong to the 2NF, indeed 3NF and BCNF. 25
Page 1 and 2: Chapter 6 Normalization Conceptual
Page 3 and 4: Remember this one Consider the foll
Page 5 and 6: Another abnormally Assume that we w
Page 7 and 8: Decomposition The solution to the a
Page 9 and 10: What have we learned 1. Decompositi
Page 11 and 12: Technically, ... ..., a functional
Page 13 and 14: FD examples Given the following val
Page 15 and 16: What do we really want We notice th
Page 17 and 18: Key is a special FD Note that the k
Page 19 and 20: Identify the FDs... Consider the ta
Page 21 and 22: The bad guy Consider the following
Page 23: What is happening As a result, we h
Page 27 and 28: The BCNF A relation schema S = (R,
Page 29 and 30: BCNF states that if this is the cas
Page 31 and 32: 4. A relation instance that is in a
Page 33 and 34: 5. BCNF relations with more than on
Page 35 and 36: 3NF could be redundant We saw earli
Page 37 and 38: A plan Since there is no redundancy
Page 39 and 40: An example Consider the following s
Page 41 and 42: An example The decomposition of Has
Page 43 and 44: A bit too late ..., which we will o
Page 45 and 46: BCNF Decomposition Let S 0 = (R, F)
Page 47 and 48: Via 3NF If we settle for 3NF, it is

Chapter 6 Normalization

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