Mapping Relational Algebra Operators into SQL Queries: A Database Case Study (original) (raw)
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Relational Algebra Interpreter in Context of Query Languages
International Journal of Computer Theory and Engineering, 2011
Relational database systems have succeeded commercially because of their openness and sturdy theoretical groundwork. The contribution of this title "Relational Algebra Interpreter in context of query languages" is presentation of new implementation in such a way so that queries written in relational algebra can be compiled into SQL and executed on a relational database system. It takes a relational algebra statement as key, does syntactic and lexical parsing on it. In the event of an error in the syntax of the expression it will forward the error to user. If the syntax is correct the relational algebra expression is converted into a SQL statement and executed on an RDBMS. This work can serve up as a basis learning Relational Algebra for different class of users, as they will be given immediate feedbacks about their queries.
Relational Algebra Interpreter
Proceedings of the 2014 International Conference on Advanced ICT (ICAICTE 2014), 2014
Relational Algebra is a procedural language that defines database in terms of algebraic expressions. It is used to explain query execution and optimization in a relational DBMS. However, the tools available to teach the concepts of Relational Algebra are limited. Most of the tools that teach database concepts are concentrated around SQL. In this paper, we introduce an application that implements five different relational operators (select, project, union, intersect and difference) by using Irony technology. This .NET web is a tool that transforms a Relational Algebraic expression into SQL queries. The resultant SQL then is used to query a database.
Relational Algebra Expression Evaluation Bachelor's Thesis
Thereby I declare that this thesis is my original work, which I have created on my own. All sources and literature used in writing the thesis, as well as any quoted material, are properly cited, including full reference to its source.
Relational Algebra and SQL Query Visualisation
2010
Abstract Relational algebra and the industry standard SQL are core topic covered in undergraduate database courses. Database management systems translate SQL statements into a procedural query plan composed with operations similar to those that arise in relational algebra. Learning relational algebra makes students familiar with this process. Moreover they understand the difference between procedural and declarative query languages.
In recent years, there has been an increasing supply of digital, pedagogical tools, known as Digital Learning Objects (DLO) – digital resources (image, film, animation, etc.) and software developed specifically for educational purposes. In the area of Computer Science, teaching Databases present a particular challenge because of a lack of quality tools to work with Relational Algebra. The present study proposes a web-based tool to support teaching and learning Relational Algebra – an important subject that is particularly difficult for students to understand. The purpose of the proposed tool is to provide an alternative method for teaching Relational Algebra operations, such as: selection, projection, union, set difference, rename, intersection, Cartesian product, natural join, division and some aggregate functions. In addition, we propose a graphic definition of a database schema (using features such as drag and drop, column highlights, lines, fields, etc.), so students can use the tool easily, and in conjunction with the theory taught regarding the definition languages (DDL) and data manipulation (DML). We intend for this tool to serve as an appropriate means for teaching and learning Relational Algebra, contributing to the development of new teaching skills, as well motivating the students in the process of learning.
Journal of Physics: Conference Series
Division operator is one of operators in Relational Algebra which is not implemented directly in SQL (Structured Query Language) standard. Therefore it is not be able to retrieve division query results with an SQL statement in the current relational database management systems (RDBMS). Database programmers have to create a complicated query to perform the task. It is the only relational algebra operators which is not implemented in ANSI SQL standard. This research aimed to study and design an algorithm named TransJoin (transformation and join) to implement it in SQL. TransJoin works to relation P(x, y) divided by Q(y) resulted R(x) through grouping and transforming each y attribute becomes P’(x, y’) and Q’(y’) and each x value is a single tuple with y’ is a composite value of y. Then, result R(x) is resulted of joining P’(x, y’) and Q’(y’) relations by matching y’ attribute. TransJoin was implemented in an open source RDBMS SQLLite. TransJoin tested and delivered valid results by co...
A Simple Approach to SQL Joins in a Relational Algebraic Notation
Join is an operation in accessing the data from table if number of tables exceeds one. Whenever we need the data which is not available from a single table, then it needs to necessitate using join operation. Sometimes join is required even if there is a single table. It all depends on the format in which we need to display the data in the user environment.
An improved division operator for relational algebra
Information Systems, 1989
Since the introduction of the relational data model, relational algebra has been used to gauge the completeness of relational query languages. As a concise language for formulating queries against relational databases, relational algebra is unmatched. Furthermore, human factor studies have shown that for difficult queries, users perform better using the procedurally-oriented relational algebra than using a non-procedural, specification-based, language such as SQL. Still, the current implementations of relational algebra in database management systems are not "friendly" when it comes to formulation of queries involving universal quantification. The algebraic operation of division normally used for this purpose is difficult for most users to comprehend and work with and is incapable of expressing queries that demand the comparison of sets of values associated with matching groups of tuples in two relations. This paper introduces a new algebraic operation, called grouped generalized division (GGD), which overcomes such shortcomings. We also show how the GGD operation can be expressed in terms of the other more "primitive" algebraic operations. As such, the implementors of algebraic languages can support the GGD operation at the user interface with minimal effort.