Unnormalized form

In database normalization, unnormalized form (UNF), also known as an unnormalized relation or non-first normal form (N1NF or NF2), is a database data model (organization of data in a database) which does not meet any of the conditions of database normalization defined by the relational model. Database systems which support unnormalized data are sometimes called non-relational or NoSQL databases. In the relational model, unnormalized relations can be considered the starting point for a process of normalization. It should not be confused with denormalization, where normalization is deliberately compromised for selected tables in a relational database. In 1970, E. F. Codd proposed the relational data model, now widely accepted as the standard data model. At that time, office automation was the major use of data storage systems, which resulted in the proposal of many NF2 data models like the Schek model, Jaeschke models (non-recursive and recursive algebra), and the Nested Table Data (NTD) model. IBM organized the first international workshop exclusively on this topic in 1987 which was held in Darmstadt, Germany. Moreover, a lot of research has been done and journals have been published to address the shortcomings of the relational model. Since the turn of the century, NoSQL databases have become popular owing to the demands of Web 2.0. Normalization to first normal form requires the initial data to be viewed as relations. In database systems relations are represented as tables. The relation view implies some constraints on the tables: No duplicate rows. In practice, this is ensured by defining one or more columns as primary keys. Rows do not have an intrinsic order. While tables have to be stored and presented in some order, this is unstable and implementation dependent. If a specific ordering needs to be represented, it has to be in the form of data, e.g. a "number" column. Columns have unique names within the same table. Each column has a domain (or data type) which defines the allowed values in the column.