Database Relations and Normal Forms
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Questions and Answers

What is the primary goal of relation decomposition?

  • To ensure each individual relation is in 2NF
  • To minimize the number of attributes in each relation
  • To ensure each individual relation is in BCNF or 3NF (correct)
  • To maximize the number of relations in the decomposition

What is the attribute preservation condition of a decomposition?

  • Each attribute in R appears in exactly two relation schemas Ri
  • Each attribute in R appears in at least one relation schema Ri (correct)
  • Each attribute in R appears in all relation schemas Ri
  • Each attribute in R appears in no relation schema Ri

Why is it not sufficient to consider individual relations in a decomposition to guarantee a good database design?

  • Because individual relations may not be in BCNF
  • Because the decomposition as a whole must be considered (correct)
  • Because individual relations may not be in 3NF
  • Because the number of relations in the decomposition is not sufficient

What is the purpose of specifying the set F of FDs that should hold on the attributes of R?

<p>To make the FDs available to the design algorithms (D)</p> Signup and view all the answers

What is the dependency preservation condition of a decomposition?

<p>FD X → Y can be inferred from the dependencies that appear in some Ri (C)</p> Signup and view all the answers

What is the result of decomposing the universal relation R into a set of relation schemas D?

<p>A set of relations that together form the relational database (D)</p> Signup and view all the answers

What is the relation EMPLOYEE_3 based on?

<p>Only tuples where Dnum is not NULL (C)</p> Signup and view all the answers

What is a challenge in normalization algorithms?

<p>They are not always deterministic (D)</p> Signup and view all the answers

What is a multivalued dependency (MVD) in a relation schema?

<p>A constraint on multiple tuples in a relation (C)</p> Signup and view all the answers

What is required to specify all the relevant dependencies among database attributes?

<p>All functional dependencies (C)</p> Signup and view all the answers

What is the goal of normalization algorithms?

<p>To achieve BCNF and preserve dependencies (D)</p> Signup and view all the answers

What is a trivial multivalued dependency (MVD)?

<p>An MVD where Y is a subset of X or X υ Y is equal to R (B)</p> Signup and view all the answers

What is a functional dependency between two sets of attributes X and Y?

<p>The value of X determines a unique value for Y (C)</p> Signup and view all the answers

What is the dependency preservation property in relational database design?

<p>A decomposition that preserves all functional dependencies (B)</p> Signup and view all the answers

What is the purpose of finding the minimal cover of a set of functional dependencies?

<p>To eliminate redundant dependencies (C)</p> Signup and view all the answers

What is the nonadditive (or lossless) join property in relational database design?

<p>A decomposition that preserves data during join (D)</p> Signup and view all the answers

What is the purpose of the inference rules for functional dependencies?

<p>To derive new functional dependencies (C)</p> Signup and view all the answers

What do functional dependencies represent in a relational database?

<p>Real-world constraints on the attributes (D)</p> Signup and view all the answers

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