Database-MySQL [3i Infotech Placement]: Sample Questions 92 - 93 of 162

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Question 92

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Appeared in Year: 2017

Describe in Detail

Essay▾

What is Entity set?

Explanation

  • An entity set is a set of entities of the same type (e. g. , all persons having an account at a bank) .
  • Entity sets need not be disjoint.
  • For example, the entity set employee (all employees of a bank) and the entity set customer (all customers of the bank) may have members in common.

Five entity sets in this section:

  • Branch: The set of all branches of a particular bank.
    • Each branch is described by the attributes branch-name, branch-city and assets.
  • Customer: The set of all people having an account at the bank.
    • Attributes are customer-name, S. I. N. , street and customer-city.
  • Employee: With attributes employee-name and phone-number.
  • Account: The set of all accounts created and maintained in the bank.
    • Attributes are account-number and balance.
  • Transaction: The set of all account transactions executed in the bank.
    • Attributes are transaction-number, date and amount.

Question 93

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Describe in Detail

Essay▾

What is Buffer Manager?

Explanation

Given Buffer Management
  • Responsible primarily for managing the operations inherent saving and loading of the blocks.
  • Reads disk pages into a main memory page as needed.
  • Used by access methods, heap files, and relational operators to read/write page.
  • Makes calls to the underlying DB class object, which actually performs these functions on disk pages.
  • Must use some techniques in order to provide good service:
    • Replacement Strategy
    • Pinned Blocks
    • Forced Output of Blocks

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