Lecture3onDataNormalization..docVIP

Lecture 3 on Data Normalization Database normalization aims to remove irregularity (abnormality) of update. The un-normal database is difficult to maintain the correctness of database after update while the normalized database schema is more user friendly for database update. On the other hand, the denormalization is the reverse of normalization. It transforms the normalized database design into un-normal form. As a result, the denormalized database is difficult to update. Nevertheless, the denormalized database can perform faster than normalized database because it requires less join operations for query. The unnormal form implies that the table tuples containing multiple values and without key value. The first normal form implies that the table tuples in atomic value, that is, single value, and with key value. The second normal form implies that all the relations are in fully functionally dependency and there is no partial functional dependency. The third normal form implies that all the relations are in fully functionally dependency, and there is no transitive functional dependency. Boyce Codd Normal Form implies that all the candidate keys in each relation are also determinant. They are also called strong third normal form, that is, they are more restricted than third normal form. The fourth normal form implies that all the relations do not have multiple multi-valued dependencies. In other words, the 2-decomposibility of multiple multi-valued dependency in a relation is decomposed into two single multi-valued dependency relations. The fifth normal form implies that all the relations do not have join dependency. In other words, the 3-decomposibility of join dependency in a relation is decomposed into three relations which can join together into an un-normal form relation with the join dependency. Functional dependency implies that a determinant can determine dependency fields. Inclusion dependency implies that a subclass data must be within its superclass d