— The first part of the exercise simply involved re-ordering the — data in the data.sql file so that tables were inserted in an — order such that there would never be references to keys that — were not already inserted into the database. — — Valid orders for populating tables: — Employee, Department, Mission, […]
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T ransactions, Recovery and Concurrency (I) 3/30/20 1 Air-line Reservation • 10 available seats vs 15 travel agents. • How do you design a robust and fair reservation system? – Insufficient resources – Fair policy to every body – Robustness 3/30/20 2 Failures Number of factors might cause failures in user requirements processing. 1. System
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Graph Algorithms (I) COMP9024: Data Structures and Algorithms Graphs (I) Contents • Graph terminology • Adjacency matrix representation • Adjacency list representation 3 Graphs ORD DFW SFO LAX 4 Graphs • A graph is a pair (V, E), where • V is a set of nodes, called vertices • E is a collection of pairs
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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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The Relational Data Model 2/14/20 1 2. The Relational Data Model • use a simple and uniform data structure: the relation • has been implemented in most commercial database systems • has a solid theoretic foundation. 2/14/20 2 2.1 Structures • In the relational model, everything is described using relations. • A relation can be
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COMP9024: Data Structures and Algorithms COMP9024: Data Structures and Algorithms Trees and Binary Search Trees Contents • Trees • Tree traversals • Binary search trees Maps and Dictionaries • A map (dictionary) is a collection of data items each of which is a pair (key, value), and supports the following major operations: find(item): find
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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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Normal Forms Normal Forms for Relational Databases 1 Normal Forms for Relational Databases • criteria for a good database design (i.e., to resolve update anomalies) • formalized by functional (or other) dependencies 2 Normal Forms: • 1NF, 2NF, 3NF (Codd 1972) • Boyce-Codd NF (1974) • Multivalued dependencies and 4NF (Zaniolo 1976 and Fagin 1977)
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Physical Database Design * Overview 1 * Overview: Database Design Data models: ER, Relational Data Model and their mapping Relational Algebra: be able to use relational algebra to answer question. Database Languages: SQL, PLpgSQL (final exam: You can read and understand SQL code and convert it to Relational Algebra Expression) Relational Database Design: Functional Dependency,
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