Cis 109 Assignment 3

1077 Words Jun 2nd, 2014 5 Pages
Logical Design
Gregory M Dowell
CIS 111
Professor Thakkar
25 February 2014

Logical Design The purpose of normalization is to create a stable set of relations is representative of the operations of an enterprise. By doing this we are able to reduce redundancy to save space and avoid inconsistencies in data. It also ensures that the design is free of certain updates, insertions, and deletion anomalies (Ricardo, 2012). With normalization as with most anything else there are advantages and disadvantages. The advantages of normalization are: ACID, which stands for atomicity, consistency, isolation, and durability. Atomicity means the transaction is a single unit. Either the entire set of actions is carried out or is not.
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This causes an inconsistency in the data since it was only updated in one location and not all locations. Insertion anomalies occur due to the impossibility to store some information unless other information is stored as well. Deletion anomalies are caused by information being deleted that may cause other information to be deleted as well. This means it may not be possible to delete some information without deleting other information as well. That is why it is important to use normalization when creating databases to help alleviate these problems. There are three stages to normalization, 1st NF, 2nd NF, and 3rd NF. In the 1st NF stage must ensure that the table has no multivalued attributes. If there are the table should be broken down into separate tables so that there are no multivalued attributes. The 2nd NF stage requires that we break the tables down even more to ensure that all attributes and functional dependency entirely to the primary key and has met all requirements of the 1st NF. Then, and only then will it be considered to have met 2nd NF requirements. To transform the database to 3rd NF you must identify the primary key in the 2nd NF table. Then we must identify functional dependencies in the relationship to ensure there are no transitive dependencies. These types of dependencies can cause insertion, deletion, and update