Database-MySQL [3i Infotech Placement]: Sample Questions 118 - 119 of 162

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Question 118

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Describe in Detail

Essay▾

What is durability in DBMS?

Explanation

Understanding of Durability
  • Durability in databases is the one type of property that ensures transactions are saved permanently and do not accidentally disappear or get erased, even during a database crash.
  • Flushing the transaction՚s log records to non-volatile storage before acknowledging commitment that achieved by durability.
  • If you are buying something from an online shop, if he system crashes , your credit card is processed and the order is placed, then that order remains in place.
  • When acknowledging commitment- durability can be achieved by flushing the transaction՚s log records to non-volatile storage.

Question 119

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Describe in Detail

Essay▾

What is Domain-Key Normal Form?

Explanation

Define Domain-Key Normal Form

Definition:

  • Domain-key normal form (DKNF) is a normal form, it is used in database normalization
  • Requires no constraints other than domain constraints and key constraints.
  • Example is Boyce-Codd normal form (BCNF) , fourth normal form, and fifth normal form
  • Avoids having general constraints in the database.
  • All database constraints simply check all attribute values in a tuple form are of the appropriate domain and that every key constraint is enforced.
  • While the domain-key normal form eliminates the problems found in most databases, it tends to be the most costly normal form to achieve.

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