CSC 4402 Final Exam Study Guide

CSC 4402 Final Exam Study Guide - CSC 4402 Page 1 of 19...

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CSC 4402 12/2/2009 Page 1 of 19 Final review Don’t forget logical & physical data independence. Review the big concepts from the midterm. There will be SQL queries on the final. We will have to draw an E-R diagram on the final. This will probably be done by being given the relation tables and constructing the E-R diagram from the relational tables. Review previous homework and answer keys. Part 4 – Database design Design process User requirement specification Conceptual design o E-R Modeling Main constructs Entities o Instance – an object o Set – set of objects sharing common characteristics (attributes) o Regular/strong vs. weak entities Weak don’t have a primary key and rely on other relations to exist Relationships o Instance o Set Attributes o Description/characterization of entity/relationship Subtype/supertype o Generalization hierarchies Mapping cardinality constraints For binary relationships we have 1-1, 1-m, m-m. o E-R diagram Entities are rectangles. Relationships are diamonds. Attributes are ellipses. Should show cardinalities on the diagram Should you use attribute set or entity set, etc. Given an E-R diagram how do you do a reduction from E-R model to the relational model. Entities are mapped to tables Foreign keys on many side, referring to one side Review the other rules
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CSC 4402 12/2/2009 Page 2 of 19 o Conceptual schema Functional requirement specification o What the system should be able to support Final stage o Logical design o Physical design Major pitfalls in database design o Redundancy o Incompleteness Logical design of relational DB (Dr. Chen’s lecture notes) o Desired properties of a good logical design Reduced redundancy Achieve representation power (i.e. completeness) Avoid loss of information o We will be required to give examples of a bad design (know at least one that violates each of the good design principles above). We should also be able to explain how to correct the problem. o Normalization is the approach used to achieve a good design. Using theory of functional dependencies First normal form (1NF) Second normal form (2NF) – not as important Third normal form (3NF) Boyce-Codd normal form (BCNF) o Trivial f.d. (i.e. x x or xy x) o Armstrong’s axioms/rules Augmentation Transitivity Projection rule Check for more in notes o Logical implication of functional dependencies Gives rise to notion of closures F.D. closures Attribute closures (w.r.t. a set of f.d.s) Candidate key (from perspective of f.d.s) – smallest set of attributes that determines all f.d.s Super key (from perspective of f.d.s) Non-key attribute Minimal cover of a set F of functional dependencies LLJ (loss-less join) decomposition Fd-preserving decomposition o Algorithms X + computation (homework 6) Minimal cover computation (homework 6) – 3 steps
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CSC 4402 Final Exam Study Guide - CSC 4402 Page 1 of 19...

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