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RDBMS Interview Questions - Part 10


A B C is a set of attributes. The functional dependency is as follows

AB -> B
AC -> C
C -> B
a) is in 1NF
b) is in 2NF
c) is in 3NF
d) is in BCNF
(a) is in 1NF since (AC)+ = { A, B, C} hence AC is the primary key. Since C B is a FD given, where neither C is a Key nor B is a prime attribute, this it is not in 3NF. Further B is not functionally dependent on key AC thus it is not in 2NF. Thus the given FDs is in 1NF.

In mapping of ERD to DFD

  • entities in ERD should correspond to an existing entity/store in DFD

    A dominant entity is the entity

  • on the 1 side in a 1 : N relationship

    Select 'NORTH', CUSTOMER From CUST_DTLS Where REGION = 'N' Order By

    CUSTOMER Union Select 'EAST', CUSTOMER From CUST_DTLS Where REGION = 'E' Order By CUSTOMER The above is Error - the ORDER BY clause. Since ORDER BY clause cannot be used in UNIONS

    What is Storage Manager ?

    It is a program module that provides the interface between the low-level data stored in database, application programs and queries submitted to the system.

    What is Buffer Manager ?

    It is a program module, which is responsible for fetching data from disk storage into main memory and deciding what data to be cache in memory.

    What is Transaction Manager ?

    It is a program module, which ensures that database, remains in a consistent state despite system failures and concurrent transaction execution proceeds without conflicting.

    What is File Manager ?

    It is a program module, which manages the allocation of space on disk storage and data structure used to represent information stored on a disk.

    What is Authorization and Integrity manager ?

    It is the program module, which tests for the satisfaction of integrity constraint and checks the authority of user to access data.

    RDBMS Interview Questions - Part 11 >>>




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