COMP9311 DATABASE SYSTEMS • Xuemin L in • Schoo l o f Compu te r Sc ience and Eng inee r i ng • Off i ce : K17 -503 • E-ma i l : l xue@cse .unsw.edu .au • Ex t : 6493 • h t tp : / /www.cse .unsw.edu .au /~ l […]
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Functional Dependency Functional Dependency 1 Functional Dependency A “good” database schema should not lead to update anomalies. • update anomalies, • functional dependencies, • Armstrong Axioms, • closures. 2 Update Anomalies Redundancy in a database means storing a piece of data more than once. Redundancy is often useful for efficiency and semantic reasons, but creates
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Relational Database Design 1 10 Relational Database Design Anomalies can be removed from relation designs by decomposing them until they are in a normal form. Several problems should be investigated regarding a decomposition. A decomposition of a relation scheme, R, is a set of relation schemes {R1, . . . ,Rn} such that Ri⊆R for
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Exercise 3 Question 1 Consider a relation R(A,B,C,D,E) with the following dependencies: AB -> C CD -> E DE -> B Is AB a candidate key of this relation? If not, is ABD? Explain your answer. Question 2 Consider the relation R, which has attributes that hold schedules of courses and sections at a university;
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Final Exam Please make sure that you always use notations consistent with lecture notes. Different notations will not be accepted. The deadline for final assessment is: SAT 8th , May 5:00 pm Please do not wait till the last minute to submit and doubt check it is successful. Question 1 (18 marks) (a) (10 marks)
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Background Information DurianPC aims to become a top-notch manufacturer of desktop and laptop computers in the Lukewarm Kingdom. The company was just formed recently but has already received abundant funding from investors all over the kingdom. The company has made a lot of decisions on the structure and operations of the company, which will be
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COMP9321 Data Services Engineering Term1, 2020 Week 2: Data Cleansing 2 *https://www.martingoodson.com/ten-ways-your-data-project-is-going-to-fail/ ** https://www.informatica.com/au/services-and-training/glossary-of-terms/data-cleansing-definition.html#fbid=eohTNIdjKaj Data Cleansing • Datasets are messy, messy data can give wrong insights (Martin Goodson’s story*) • Cleansing/Cleaning data “find and remove or correct data that detracts from the quality, and thus the usability, of data. The goal of data cleansing is
Data Mining Third Edition The Morgan Kaufmann Series in Data Management Systems (Selected Titles) Joe Celko’s Data, Measurements, and Standards in SQL Joe Celko Information Modeling and Relational Databases, 2nd Edition Terry Halpin, Tony Morgan Joe Celko’s Thinking in Sets Joe Celko Business Metadata Bill Inmon, Bonnie O’Neil, Lowell Fryman Unleashing Web 2.0 Gottfried Vossen,
Detecting Functional Dependencies 21.5.2013 Felix Naumann 2 Overview ■ Functional Dependencies ■ TANE □ Candidate sets □ Pruning Algorithm □ Dependency checking □ Approximate FDs ■ FD_Mine ■ Conditional FDs Felix Naumann | Profiling & Cleansing | Summer 2013 3 Definition – Functional Dependency ■ „X → A“ is a statement about a relation R:
School of Computing and Information Systems INFO20003 Database Systems SAMPLE EXAM Reading Time: 15 minutes Writing time: 120 minutes This paper has 14 pages including this page Authorised Materials Calculators: Casio fx82 calculators are permitted Instructions to Invigilators The examination paper IS TO REMAIN in the examination room Students are to be provided