FIRST NORMAL FORM_122147.Database Normalizationpptx

Normalization

1. FIRST NORMAL FORM TINYIKO ERIC SHAKIR 1

2. INTRODUCTION. First normal form was introduced by E.F. Codd in the paper "A Relational Model of Data for Large Shared Data Banks", although it was initially just called "Normal Form". It was renamed to "First Normal Form" when additional normal forms were introduced in the paper Further Normalization of the Relational Mode. Relational database design ultimately produces a set of relations. The implicit goals of the design activity are: information preservation and minimum redundancy. 2

3. Normalization Normalization; is a database technique that reduces data redundancy and eliminates undesirable characteristics like insertion, update and Deletion Anomalies. Normalization rules divides larger tables into smaller tables that links those using relationships. The purpose of normalization is to eliminate redundant data and ensure data is stored logically. Normalization increase clarity and is achieved by following a set of rules called “forms” in creating a database The purpose of this normalization is to increase flexibility and data independence, and to simplify the data language. It also opens the door to further normalization, which eliminates redundancy and anomalies. 3

4. Database Normalization entails organizing the columns (attributes) and tables (relations) of a database to ensure that their dependencies are properly enforced by database integrity constraints. It is accomplished by applying some formal rules either by a process of synthesis (creating a new database design) or decomposition (improving an existing database design). 4

5. FIRST NORMAL FORM. The First normal form (1NF) is a property of a relation in a relational database. A relation is in first normal form if and only if no attribute domain has relations as elements . Or more informally, that no table column can have tables as values or no repeating groups. The first normal form is one of the minimal requirements in the database normalization processes. The first step in confirming 1NF is modifying multivalued columns to make sure that each column in a table does not take more than one entry. 5

6. The first normal form states that: • Every column in the table must be unique • Separate tables must be created for each set of related data • Each table must be identified with a unique column or concatenated columns called the primary key • No rows may be duplicated • no columns may be duplicated • no row/column intersections contain a null value • no row/column intersections contain multivalued fields • Each cell must contain only a single (atomic) value. • Every column in the table must be uniquely named. • All values in a column must pertain to the same domain. 6

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9. 1NF tables as representations of relations According to Date's definition, a table is in first normal form if and only if it is isomorphic to some relation, which means, specifically, that it satisfies the following five conditions 1. There's no top-to-bottom ordering to the rows. 2. There's no left-to-right ordering to the columns. 3. There are no duplicate rows. 4. Every row-and-column intersection contains exactly one value from the applicable domain (and nothing else). 5. All columns are regular [i.e. rows have no hidden components such as row IDs, object IDs, or hidden timestamps]. 9

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12. Objectives A basic objective of the first normal form defined by Codd in 1970 was to permit data to be queried and manipulated using a "universal data sub-language" grounded in first-order logic SQL is an example of such a data sub-language. 1. To free the collection of relations from undesirable insertion, update and deletion dependencies. 2. To reduce the need for restructuring the collection of relations, as new types of data are introduced, and thus increase the life span of application programs. 3. To make the relational model more informative to users. 4. To make the collection of relations neutral to the query statistics, where these statistics are liable to change as time goes by. 12

13. DRAWBACKS & CRITICISM • Performance for certain operations. In a hierarchical model, nested records are physically stored after the parent record, which means a whole sub-tree can be retrieved in a single read operation. In a 1NF form, it will require a join operation per record type, which can be costly, especially for complex trees. For this reason document databases eschew 1NF. • Object-oriented languages represent runtime state as trees or directed graphs of objects connected by pointers or references. This does not map cleanly to a 1NF relational database, a problem sometimes called the Object-Relational Impedance Mismatch. • 1NF has been interpreted as not allowing complex data types for values. This is open to interpretation though. 13