Sql Interview Question and Answers

66. What is a Database instance?
  A database instance (Server) is a set of memory structure and background processes that access a set of database files.
 
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67. What are Roles?
  Roles are named groups of related privileges that are granted to users or other roles.
 
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68. What is SQLPlus?
  SQLPlus is an application that recognizes & executes SQL commands & specialized SQL*Plus commands that can customize reports, provide help & edit facility & maintain system variables.
 
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69. What is the difference between normalization and denormalization?
  Normalizing data means eliminating redundant information from a table and organizing the data so that future changes to the table are easier.

Denormalization means allowing redundancy in a table. The main benefit of denormalization is improved performance with simplified data retrieval and manipulation.
 
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70. What is a trigger?
  Triggers are stored procedures created in order to enforce integrity rules in a database. A trigger is executed every time a data-modification operation occurs (i.e., insert, update or delete).
Triggers are executed automatically on occurance of one of the data-modification operations.
 
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