Database-MySQL [3i Infotech Placement]: Sample Questions 110 - 112 of 162

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Question 110

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Short Answer▾

When is a functional dependency F said to be minimal?

Explanation

F to be minimal if it satisfies the following conditions:

  • Every dependency in F has a single attribute for its right hand side.
  • It cannot replace any dependency X ⇾ A in F with a dependency Y ⇾ A where Y is a proper subset of X and still have a set of dependency that is equivalent to F.
  • We cannot remove any dependency from F and still have set of dependency that is equivalent to F.

Question 111

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Describe in Detail

Essay▾

What is the difference between “translate” and “replace”

Explanation

Difference between Translate and Replace
REPLACETRANSLATE
  • REPLACE replaces every instance of a set of characters with another set of characters
  • TRANSLATE replaces single characters at a time
  • REPLACE provides functionality related to that provided by the TRANSLATE function.
  • TRANSLATE provides single-character, one-to-one substitution.
  • Returns string if no match found
  • Returns null if no match found

Question 112

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Describe in Detail

Essay▾

What is Relational Calculus?

Explanation

  • Relational calculus is an query language which is non procedural, and instead of algebra it uses mathematical predicate calculus.
  • The relational calculus is not the same like that of differential and integral calculus in mathematics, but takes its name from a branch of symbolic logic termed as predicate calculus.
  • When applied to databases, it is found in two forms. These are
    • Tuple relational calculus which was originally proposed by Codd in the year 1972 and
    • Domain relational calculus which was proposed by Lacroix and Pirotte in the year 1977

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