Search results
Results from the WOW.Com Content Network
The third normal form (3NF) is a normal form used in database normalization. 3NF was originally defined by E. F. Codd in 1971. [2] Codd's definition states that a table is in 3NF if and only if both of the following conditions hold: The relation R (table) is in second normal form (2NF).
The elementary key normal form (EKNF) falls strictly between 3NF and BCNF and is not much discussed in the literature. It is intended "to capture the salient qualities of both 3NF and BCNF" while avoiding the problems of both (namely, that 3NF is "too forgiving" and BCNF is "prone to computational complexity"). Since it is rarely mentioned in ...
Normalization consists of normal forms that are 1NF, 2NF, 3NF, Boyce-Codd NF (3.5NF), 4NF, 5NF and 6NF. Document databases take a different approach. A document that is stored in such a database, typically would contain more than one normalized data unit and often the relationships between the units as well.
Second normal form (2NF), in database normalization, is a normal form. A relation is in the second normal form if it fulfills the following two requirements: It is in first normal form. It does not have any non-prime attribute that is functionally dependent on any proper subset of any candidate key of the relation (i.e. it lacks partial ...
In the Today's court bookings table, there are no non-prime attributes: that is, all attributes belong to some candidate key. Therefore, the table adheres to both 2NF and 3NF. The table does not adhere to BCNF. This is because of the dependency Rate type → Court in which the determining attribute is Rate type, on which Court depends.
So if you say that the higest normal form of a table is 2NF, this means that it is not 3NF and that you can also say it is 1NF (because 2NF meets all lower requirements.) On the other hand most 3NF tables meet the requirements of, say, 4NF, so 3NF is not the HNF for most 3NF tables.--Boson 21:15, 10 June 2014 (UTC)
Denormalization is a strategy used on a previously-normalized database to increase performance. In computing , denormalization is the process of trying to improve the read performance of a database , at the expense of losing some write performance, by adding redundant copies of data or by grouping data.
A hierarchical database model is a data model in which the data is organized into a tree-like structure. The data are stored as records which is a collection of one or more fields . Each field contains a single value, and the collection of fields in a record defines its type .