Multivalued or NFNF Databases
Multivalued or NFNF databases violate 1NF by allowing a column to contain more than one scalar value. This model has been use for decades in commercial products but did not get a theoretical basis until much later. This chapter discusses multivalued databases.
COBOL; Pick; nonfirst normal form (NFNF); first normal form (1NF)
RDBMS is based on first normal form (1NF), which assumes that data is kept in scalar values in columns that are kept in rows and those records have the same structure. The multivalued model allows tables to be nested inside columns. They have a niche market that is not well known to SQL programmers. There is an algebra for this data model that is just ...