Lecture

Relational Query Optimization

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Description

This lecture covers the process of relational query optimization, including logical and physical query plans, query transformations, equivalences in relational algebra, cost estimation, statistics and catalogs, size estimation, reduction factors, and the System R strategy. The instructor explains the phases of query optimization, the importance of query blocks, and the selection-project-join optimization core. Various examples are provided to illustrate the concepts, such as result size estimation for selections and natural joins. The lecture concludes with an overview of the query optimization phases and the improved strategy used in System R.

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Ontological neighbourhood

Computer engineering

Databases: Relational databases

Related concepts (32)

Query optimization

Query optimization is a feature of many relational database management systems and other databases such as NoSQL and graph databases. The query optimizer attempts to determine the most efficient way to execute a given query by considering the possible query plans. Generally, the query optimizer cannot be accessed directly by users: once queries are submitted to the database server, and parsed by the parser, they are then passed to the query optimizer where optimization occurs.

Relational algebra

In database theory, relational algebra is a theory that uses algebraic structures for modeling data, and defining queries on it with a well founded semantics. The theory was introduced by Edgar F. Codd. The main application of relational algebra is to provide a theoretical foundation for relational databases, particularly query languages for such databases, chief among which is SQL. Relational databases store tabular data represented as relations. Queries over relational databases often likewise return tabular data represented as relations.

Presentation slide

A slide is a single page of a presentation. Collectively, a group of slides may be known as a slide deck. A slide show is an exposition of a series of slides or images in an electronic device or in a projection screen. Before the advent of the personal computer, a presentation slide could be a 35 mm slide viewed with a slide projector or a transparency viewed with an overhead projector. In the digital age, a slide most commonly refers to a single page developed using a presentation program such as MS PowerPoint, Apple Keynote, Google Slides, Apache OpenOffice or LibreOffice.

Microsoft Office 2007

Microsoft Office 2007 (codenamed Office 12) is an office suite for Windows, developed and published by Microsoft. It was officially revealed on March 9, 2006 and was the 12th version of Microsoft Office. It was released to manufacturing on November 3, 2006; it was subsequently made available to volume license customers on November 30, 2006, and later to retail on January 30, 2007, shortly after the completion of Windows Vista. The ninth major release of Office for Windows, Office 2007 was preceded by Office 2003 and succeeded by Office 2010.

Hash join

The hash join is an example of a join algorithm and is used in the implementation of a relational database management system. All variants of hash join algorithms involve building hash tables from the tuples of one or both of the joined relations, and subsequently probing those tables so that only tuples with the same hash code need to be compared for equality in equijoins. Hash joins are typically more efficient than nested loops joins, except when the probe side of the join is very small.

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