Query Language For Relational Databases Research Articles

Moving selections into linear least fixpoint queries

Efficient least-fixpoint query evaluation is crucial to using logic as the query language for relational databases. The authors present a selection transposition algorithm that allows selections that are conjunctions of the predicates of the form column theta value to be evaluated ahead of the least-fixpoint operator while processing linear recursive queries. It is also shown that the algorithm transposes the strongest possible selection.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Extending relational algebra and relational calculus with set-valued attributes and aggregate functions

In commercial network database management systems, set-valued fields and aggregate functions are commonly supported. However, the relational database model, as defined by Codd, does not include set-valued attributes or aggregate functions. Recently, Klug extended the relational model by incorporating aggregate functions and by defining relational algebra and calculus languages. In this paper, relational algebra and relational calculus database query languages (as defined by Klug) are extended to manipulate set-valued attributes and to utilize aggregate functions. The expressive power of the extended languages is shown to be equivalent. We extend the relational algebra with three new operators, namely, pack, unpack, and aggregation-by-template. The extended languages form a theoretical framework for statistical database query languages.

Montage: a system for three-dimensional reconstruction by personal computer

This paper describes a simplified system for serial section three-dimensional (3-D) reconstruction. A set of 9 software programs runs on a standard personal computer and produces camera-ready illustrations suitable for publication. The user enters trace points on a digitizing tablet from sections that have been already aligned. A 3-D view of the reconstructed object is generated which can be displayed with hidden lines removed. Analysis of volume, surface area and autoradiographic grain density are performed automatically. A relational database query language allows display and analysis of a selected subset of the data. The system runs under the UNIX operating system which allows the programs to be easily transported to new hardware or modified for other purposes.

Using FP as a query language for relational data-bases

FP is the programming language defined by J. Backus to demonstrate the virtues of functional programming as opposed to conventional programming in Von Neumann-like languages. In this paper we investigate the use of FP in the framework of relational data bases. In particular, we show how the language can be used to define base relations, to derive views from a collection of relations, and to express complex database queries. The language provides all capabilities of pure algebraic relational languages, but is considerably more powerful. As such, it can be used as a formal specification language to describe the semantics of queries expressed in relational languages, such as Query-By-Example. In addition the algebra of FP programs allows one to formally prove properties of such queries.