Database-MySQL [3i Infotech Placement]: Sample Questions 86 - 87 of 162

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Question 86


Describe in Detail


What is database Trigger?


Define What is Trigger
  • A database trigger is stored code that is executed immediately after a predefined event.
  • It is used to ensure the coordinated performance of related actions.
  • Although implementation varies, all major relational databases support triggers.
  • When an associated DML statement is executed a trigger is triggered automatically.
  • Triggers are used to maintain the referential integrity of data by changing the data in a systematic fashion.
  • Triggers help the database designer ensure certain actions, such as maintaining an audit file, are completed regardless of which program or user makes changes to the data.

Types of Triggers:

  • Row Level Triggers
  • Statement Level Triggers
  • Before Triggers
  • After Triggers
Types of Triggers

Question 87


Describe in Detail


What is Storage Manager?


Explanation of Storage of Manager
  • Storage manager is a program module that provides the interface between the low-level data stored in the database and the application programs and queries submitted to the system.

    It usually contains something like the following module:

    • The Buffer Manager
    • Low-level I/O subsystem
    • The transaction and recovery manager
    • Index manager
    • The base table manager
    • Top-level APIs

Components of the Storage Manager

Authorization and Integrity Manager:

  • Tests the integrity constrains
  • Checks the authorization of users to access data.

Transaction Manager:

  • Ensures that no kind of change brought to the database until a transaction is completed totally.

File Manager:

  • Manages the allocation of space on disk storage and the data structures to represent information stored on disk.

Buffer Manager:

  • Cecides which data needs to be cached in main memory and then fetches it up in main memory.
  • Important as it defines the speed at which the database can be used.

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