First normal form

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First normal form (1NF) is the most basic level of database normalization defined by English computer scientist Edgar F. Codd, the inventor of the relational database. A relation (or a table, in SQL) can be said to be in first normal form if each field is atomic, containing a single value rather than a set of values or a nested table. In other words, a relation complies with first normal form if no attribute domain (the set of values allowed in a given column) has relations as elements. Most relational database management systems do not support creating or using table-valued columns, which means most relational databases will be in first normal form by necessity. Otherwise, normalization to 1NF involves eliminating nested relations by breaking them up into separate relations associated with each other using foreign keys. This process is a necessary step when moving data from a non-relational (or NoSQL) database, such as one using a hierarchical or document-oriented model, to a relational...

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