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Database Normalization A technique of organizing data is known as database normalization. It is a systematic approach of decomposing tables to eliminate data redundancy and undesirable characteristics like Insertion, Update and Deletion Anamolies. There is a multi-step process followed that puts data into tabular form by removing duplicated data from the relation tables. It is mainly used for two purposes: 1. Eliminating the redundant (useless) data. 2. Ensuring data dependencies make sense i.e data is logically stored. 1 NF: - In this form, no two Rows of data must contain a repeating group of information, i.e. each set of column must have a unique value, such that multiple columns cannot be used to fetch the same row. - Every table in the database should be organized into rows, and each row should have a primary key that distinguishes it as unique. - The Primary key is usually a single column, but sometimes a combination of more than one column is used to create a single primary key. 2NF: - In this form there must not be any partial dependency of any column on the primary key. - It means that for a table that has concatenated primary key, each column in the table that is not part of the primary key must depend upon the entire concatenated key for its existence. - A table fails Second normal form when any column depends only on one part of the concatenated key. 3NF: - A table that is in 1NF and 2NF, in which no non primary key attribute is transitively dependent on the primary key. BCNF: - BCNF was developed by Raymond F. Boyce and Edgar F. Codd in 1974. - It is a slightly stronger version of the third normal form (3NF). - It deals with certain types of anomaly that is not handled by 3NF. - A 3NF table which does not have multiple overlapping candidate keys is said to be in BCNF. - A table is in BCNF if and only if every determinant is a candidate key. BCNF is a stronger form of 3NF. The difference between 3NF and BCNF is that for a Functional dependency A --> B, 3NF allows this dependency in a table if attribute B is a primary key attribute and attribute A is not a candidate key, where as BCNF insists that for this dependency to remain in a table, attribute A must be a candidate key. 4NF: - 4NF is a stronger normal form than BCNF as it prevents tables from containing nontrival Multi-Valued Dependencies (MVDs) and hence data redendancy. - It is the next level of normalization after Boyce–Codd normal form (BCNF). - Whereas the second, third, and Boyce–Codd normal forms are concerned with functional dependencies, 4NF is concerned with a more general type of dependency known as a multivalued dependency. - The normalization of BCNF tables to 4NF involves the removal of MVDs from the table by placing the attribute's in a new table along with the copy of the determinants. 5NF: - 5NF is also called Project-Join Normal Form(PJRF) and specifies that a 5NF table has no Join dependency. Prajakta Pandit 03-14-2017 01:35 AM

Am I Stupid? If you dont know that,fourth normal form is nothing but Boyce Codd then why you are posting such a questions? Pranav Kadam 07-7-2016 07:11 PM

Explanation. Answer : Boyce Codd. Boyce-Codd Normal Form (BCNF) is one of the forms of database normalization. A database table is in BCNF if and only if there are no non-trivial functional dependencies of attributes on anything other than a superset of a candidate key. Jayesh Sonar 03-2-2015 02:35 AM

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