SQL/NF: A query language for ¬1NF relational databases

摘要

There is growing interest in abandoning the first-normal-form assumption on which the relational database model is based. This interest has developed from a desire to extend the applicability of the relational model beyond traditional data-processing application. In this paper, we extend one of the most widely used relational query languages, SQL, to operate on non-first-normal-form relations. In this framework, well allow attributes to be relation-valued as well as atomic-valued (e.g. integer or character). A relation which occurs as the value of an attribute in a tuple of another relation is said to be nested. Our extended language, called SQL/NF, includes all of the power of standard SQL as well as the ability to define nested relations in the data definition language and query these relations directly in the extended data manipulation language. A variety of improvements are made to SQL; the syntax is simplified and useless constructs and arbitrary restrictions are removed.