What is Data Normalization ? Define 1st NF ,2nd NF , 3rd NF , BCNF, 4th NF and 5th NF in DBMS

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 Q. What is  First Normal Form (1 NF )?

The domain of attribute must include only atomic values.

Q. What is Second Normal Form ( 2NF)?

A relation schema R is in 2NF if it is in 1NF and every non-prime attribute A in R is fully functionally dependent on primary key.

                                                                           

Q. What is Third Normal Form (3NF)?

A relation schema R is in 3NF if it is in 2NF and for every FD X A either of the following is true 

1. X is a Super-key of R.

2. A is a prime attribute of R.

In other words, if every non prime attribute is non-transitively dependent on primary key.

Frequently Asked Tough Database DBMS job interview Questions Answers & Solve Paper

 Q. Explain the meaning of the expression ACID transaction.

ACID means Atomic, Consistency, Isolation, Durability, so when any transaction happen it should be Atomic that is it should either be complete or fully incomplete. There should not be anything like Semi complete. The Database State should remain consistent after the completion of the transaction. If there are more than one Transaction then the transaction should be scheduled in such a fashion that they remain in Isolation of one another. Durability means that Once a transaction commits, its effects will persist even if there are system failures.

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Q. Explain the difference between an explicit and an implicit lock.

Explicit Lock :- Lock is explicitly requested for a record or table.

Implicit Lock :- Lock is implied but is not acquired.

Q. Explain how a database could be recovered via reprocessing. Why is this generally not feasible?